Solar Panels on House

Joey the lips

Hi Folks,

Have been considering going solar as an investment. I am not loaded but consider it like a retirement plan anything invested now will repay when I am retireing.

Any way, My house front is south south East faceing and my back north north west faceing. I also have a gable taking up half of the front.

What is my options for solar? I half know the answer but would appreciate all opinions. Thanks

quentingargan

Hi Joey,

I guess the first thing I would do is put in an application for the grant while I made up my mind. You can apply for the grant from SEI based on any system and/or installer and you are entitled to put in different panels from a different installer later. You never know when the funding from a scheme like this might get reduced or even axed.

Beyond that, in most cases some sort of site visit is required, or at least a copy of the plans of the house and a phone consultation, but the following are the key pointers....

Assuming you are moving towards retirement, I assume there are no further children on the horizon, so your hot water use is not going to increase further.

A SSE facing roof at a pitch of 45 degrees is within 5% to 10% of optimum in terms of performance. But beyond that, there are so many factors that would determine the kind of system you would install including;

• How many people there are using hot water
• Whether they use showers or baths (or if you like to peel your spuds in warm water...)
• Time of use of hot water (if the house is occupied during the day, you need more hot water earlier in the day and thus a different ratio between panels and cylinder size may be required)
• The extent of insulation of your house (if your house is very well insulated, the boiler is off until October, so you want your panels to have a longer season - that my push you towards tubes instead of flatplate as they work better in cold and cloudy weather and you don't want to switch on the boiler too often just for hot water)
• If you are going for a large panel to cylinder ratio to maximise your season, you definitely need a heat dump for your system. I personally believe they should be used at all times, but this is disputed by other posters here.
• Whether you have hard water or not (I like to bring the cylinder to 85 degrees or so, increasing effective storage, but not if limescale is going to destroy the coils as a result, in which case you may need a larger cylinder)
• If your water isn't hard, is it acidic? This would shorten the life of copper cylinders and push you towards stainless.
• Whether your house has pressurised hot water already (which would mean a stainless cylinder - stainless 300L cylinders are not much more expensive than 200L, but copper 200L cylinders are cheaper).
• Whether your hotpress can take the extra weight of a large cylinder
• You mention that you also have a south facing gable. I assume this is a hip roof which may shade your panel for some of the time. Depending on the location of the hotpress within the house, you would normally try to get the panel high and as far away from this shading as possible, but it might mean that you lose the sun for some of the time and would need a larger panel to compensate for this loss.

Generally, the quickest return is on a modest system which is in pretty full time use. The grants tend to distort this by paying per sq M which means that the extra panels are pretty well free up to a maximum of 6 sqM (which is why that size has, quite inapprorpriately, become an industry norm).

I'm sure there are things I have left out, but as I say, a site visit is normally required.

However, of all the renewable systems, solar has the fastest payback. There is lower hanging fruit which should be picked first, such as attic insulation, windows, draught proofing etc., but I assume you have all that in place. Payback time for all of these depends on whether or not energy prices continue to rise. You will see people claiming payback of 5 years - that't nonsense in my opinion, but if you get a payback time of 12 years or so, that is a return in investment of over 8% at todays energy prices and better than most other secure investments available.

gizmo555

quentingargan wrote: »

However, of all the renewable systems, solar has the fastest payback.

Quentin, can you please outline the calculations supporting this conclusion, comparing solar to, say, air or ground source heat pumps, or wood pellet/chip boilers (all of which, like solar, attract grant aid)?

quentingargan wrote: »

but if you get a payback time of 12 years or so, that is a return in investment of over 8% at todays energy prices and better than most other secure investments available.

Can you please also outline the calculations and assumptions on domestic hot water use, solar hot water system costs, and the cost of non-renewable energy sources which would lead you to believe a 12 year payback period is achievable?

quentingargan

gizmo555 wrote: »

Quentin, can you please outline the calculations supporting this conclusion, comparing solar to, say, air or ground source heat pumps, or wood pellet/chip boilers (all of which, like solar, attract grant aid)?

Heat pumps aren't a renewable, and won't be until such time as we get a substantial chunk of our electricity from renewables. That may happen. In the meantime, while an air to water system may produce 3kw of heat from 1kw of electricity, the gain is questionable because down the power line, someone is using not much less than 3kw of gas to produce 1kw of electricity.

I am also disappointed that most geothermal systems are not installed with sufficient buffer tank capacity to ensure that they only need to run at night on off-peak power. If they were, they would facilitate the introduction of more renewable energy onto the grid, but that's a rant for another day and a bit off the subject perhaps.

Pellet stoves are a different matter, and in some cases you are right - they can produce a better financial return than solar, depending on the efficiency of the system they are replacing. However, the long-term return on investment is difficult to calculate, because it is likely that pellet prices will rise in line with general energy prices. It is also hard to compare pellets because some people have suitable bulk storage.

gizmo555 wrote: »

Can you please also outline the calculations and assumptions on domestic hot water use, solar hot water system costs, and the cost of non-renewable energy sources which would lead you to believe a 12 year payback period is achievable?

I was careful not to actually promise a 12 year payback. You can't generalise on payback, because if someone has a very efficient condensing combi-boiler, their summertime hot water is a lot cheaper than someone using an immersion, or an old boiler, out in the shed heating boiler, pipes etc., just to get 120L of hot water in the hotpress.

gizmo555

quentingargan wrote: »

Heat pumps aren't a renewable, and won't be until such time as we get a substantial chunk of our electricity from renewables. That may happen. In the meantime, while an air to water system may produce 3kw of heat from 1kw of electricity, the gain is questionable because down the power line, someone is using not much less than 3kw of gas to produce 1kw of electricity.

Not all electricity comes from gas, and if you choose to get your supply from Airtricity, it's 79% renewably sourced.

quentingargan wrote: »

Pellet stoves are a different matter, and in some cases you are right - they can produce a better financial return than solar, depending on the efficiency of the system they are replacing. However, the long-term return on investment is difficult to calculate, because it is likely that pellet prices will rise in line with general energy prices. It is also hard to compare pellets because some people have suitable bulk storage.

Well, you stated without qualification that "of all the renewable systems, solar has the fastest payback". Does it or doesn't it?

quentingargan wrote: »

I was careful not to actually promise a 12 year payback.

No, but you implied it was achievable, can you elaborate under what circumstances you think it could be? What size and installed cost would a system which could pay for itself in 12 years be, how much energy would it be producing and what do you assume the source and unit cost of that energy would otherwise have been?

quentingargan

gizmo555 wrote: »

Not all electricity comes from gas, and if you choose to get your supply from Airtricity, it's 79% renewably sourced.

Obviously Airtricity buys its own juice first to sell on, but regardless, if you buy electricity, the overall mix on the grid comes from various sources, very little of which is currently renewable. If you buy your power from Airtricity and switch off your immersion, someone else gets that wind power and somewhere else another fossil fuel generator has less demand. I was being charitable citing gas - some of it comes from peat and coal too.

gizmo555 wrote: »

Well, you stated without qualification that "of all the renewable systems, solar has the fastest payback". Does it or doesn't it?

OK - you may have me on this inasmuch as there may be some pellet systems that have a quicker payback, provided their durability works out as promised, and pellet prices don't rise. In fairness, I am one of the few solar/wind people who would tell people straight that the low hanging fruit is insulation and draught proofing. There may be occasions where pellet is ahead of solar on payback time.

gizmo555 wrote: »

No, but you implied it was achievable, can you elaborate under what circumstances you think it could be? What size and installed cost would a system which could pay for itself in 12 years be, how much energy would it be producing and what do you assume the source and unit cost of that energy would otherwise have been?

We usually install 40 tubes /200L cylinder for around €4,500, less grant = €3400 nett. TSOL software modelling shows that this will put 1828 KwHr into the cylinder per annum. If that were electricity at 16c per KwHr, it would pay back €3500 over 12 years.

OK, some of the time the energy displaced may be oil or gas at a lower price, but half the price of the work is replacing the cylinder, usually a badly insulated unit, with a highly efficient insulated one, so there are additional year-round savings on the oil or gas.

Also, that's a modest system. Larger systems are proportionally cheaper so the payback might be better.

You are right to question the figures and you could also say that while this is "achievable", in most cases there would be more oil/gas in the mix etc., or that the housholder could use off-peak electricity, pellets etc. However, I believe that energy prices from all sources will rise dramatically over the coming decade and that in practice a payback of 12 years or less is what will actually be achieved. Try indexing energy prices at 5 or 10% per annum and see what that does to any figures you choose to use.

gizmo555

quentingargan wrote: »

We usually install 40 tubes /200L cylinder for around €4,500, less grant = €3400 nett. TSOL software modelling shows that this will put 1828 KwHr into the cylinder per annum. If that were electricity at 16c per KwHr, it would pay back €3500 over 12 years.

OK, some of the time the energy displaced may be oil or gas at a lower price, but half the price of the work is replacing the cylinder, usually a badly insulated unit, with a highly efficient insulated one, so there are additional year-round savings on the oil or gas.

Also, that's a modest system. Larger systems are proportionally cheaper so the payback might be better.

You are right to question the figures and you could also say that while this is "achievable", in most cases there would be more oil/gas in the mix etc., or that the housholder could use off-peak electricity, pellets etc. However, I believe that energy prices from all sources will rise dramatically over the coming decade and that in practice a payback of 12 years or less is what will actually be achieved. Try indexing energy prices at 5 or 10% per annum and see what that does to any figures you choose to use.

Quentin, you and I have been over this ground before, but for someone who is really using this much standard rate electricity to heat water, the solution is not a €3,400 solar system, but a switch to a night rate meter which ESB Networks will do for nothing. This would reduce the unit cost per kWh to around 7.6c (VAT inc) if one also switched supplier to Airtricity or Bord Gais. This would reduce your prospective savings to about €140 p.a. and double your payback period to almost 25 years. Now, it's true that the night rate tariff would incur a higher standing charge and daytime unit rate, but these could easily be recouped by running appliances like washing machines, dishwashers and clothes dryers at night. The cost of running fridges and freezers would likewise reduce. I've done this myself and I know from experience that it works in practice. This is also an environmentally sound step to take, as it helps even out electricity demand over the 24 hours, which in turn helps electricity generators limit the amount of polluting baseload generating capacity they need.

As for future energy prices, you may be right, but only time will tell. It's only by assuming steady 10% inflation in electricity prices over 14 years that one could come close to your postulated payback period. We're certainly nowhere near that at present. In the meantime and at current prices, far from having the "fastest payback" solar hot water systems are possibly the least cost-effective energy efficiency measure around.

Joey the lips

Night rates now there is an option! Figuring from this it makes sense to look at the night rate option. Thats fine but the only thing you could run at night is the dishwasher and washing machine dryer. Granted this is a sizeable chunk of applience who is going to stay up to run this.

What i was looking for is information on suitability and rough costings based on house size direction. The usuage will be 2 adults 3 children typical family.

But i see your point. A stored cylinder of water produced in the early hours of the morning could actually make the payback on solar a lot longer!

Interesting. I will get some quotes on solar and compare

gizmo555

Joey the lips wrote: »

Night rates now there is an option! Figuring from this it makes sense to look at the night rate option. Thats fine but the only thing you could run at night is the dishwasher and washing machine dryer. Granted this is a sizeable chunk of applience who is going to stay up to run this.

Well, many of these come with a start delay function which allows you to set the programme but delay the start for however long you need to benefit from the night rate. If you have existing appliances without this function, a plug-in timer from Woodies costs a fiver. Bear in mind that these appliances (especially with your household size) account for a significant fraction of domestic hot water usage, but because they usually only have a cold water inlet, cannot use hot water from a solar system. The other things which are running 24x7 are fridges and freezers, where you would see some savings too.

quentingargan

I agree that all households should have night rate electricity. To my mind it is a no-brainer.

However, unless you use hot water during the daytime, and use less than 100L of hot water per day, you will still need to change your cylinder to store enough off-peak hot water. Also, unless you already have a proper double insulated cylinder, it won't hold the heat from 8.00am until the following evening when you may want to have a bath.

Changing the cylinder in many houses is not much less than half the price of the complete system as you won't get any grant for this bit. So while it halves the cost of the hot water you are replacing, it also halves the cost of the installation.

I think that still leaves solar in the ball-park for most households.

gizmo555

quentingargan wrote: »

I agree that all households should have night rate electricity. To my mind it is a no-brainer.

Well, if you accept this then you have to accept that a 12 year payback on solar where a "no-brainer" night rate meter is installed is unachievable at current prices.

quentingargan wrote: »

However, unless you use hot water during the daytime, and use less than 100L of hot water per day, you will still need to change your cylinder to store enough off-peak hot water.

There's more than one way to skin this cat. To begin with, if one takes Seamus Hoyne of the Tipperary Institute's estimate of a medium level of consumption of 50lt per person, Joey's household would need 250lt.

http://web.archive.org/web/20071119040525/http://www.ilsu.ie/documents/SemRE/SHSolar.pdf

However, 50lt is due to washing machines and dishwashers, which is generally speaking not substitutable with solar hot water, but on the other hand can be obtained from night rate electricity. The remaining hot water requirement is now 200lt.

Next, a great many houses would have existing Triton or similar electric showers installed. Night rate electricity is available until 8am in winter and 9am in summer. Most working people would be up and have had a morning shower within the night rate period. These showers have other advantages: they heat only the exact amount of water required; they heat it at the point of use so there's no heat loss in the pipework; and they heat it on demand, so you doesn't have to worry about leaving enough hot water for others coming after you. Let's say a shower each for the parents at 35lt, that leaves a balance of 130lt.

quentingargan wrote: »

Also, unless you already have a proper double insulated cylinder, it won't hold the heat from 8.00am until the following evening when you may want to have a bath.

In my personal experience, an ordinary copper cylinder with factory-fitted spray on foam insulation will keep water heated overnight piping hot right through the day until evening.

quentingargan wrote: »

Changing the cylinder in many houses is not much less than half the price of the complete system as you won't get any grant for this bit. So while it halves the cost of the hot water you are replacing, it also halves the cost of the installation.

If it's not already there, a 140lt or 160lt copper cylinder with foam insulation could be installed for a fraction of the €1,700 you allocate to the cost of a cylinder in your estimate - probably about €500 or €600. If you were getting a plumber in to do the type of heating control work for which a €500 grant is now available, you could likely do a better deal.

quentingargan wrote: »

I think that still leaves solar in the ball-park for most households.

I really don't see how. And as someone else - sinnerboy I think - has often pointed out here, there's a reason why domestic-scale renewables are compulsory in the latest building regs. If they made reasonable economic sense, there would be no need for compulsion. That said, I accept there is more to it than pure economics and presumably Joey, like me, wants to leave a habitable world for his children and grandchildren. I'm also not saying no-one should install solar hot water. I just think, firstly they should make sure they have taken every other energy efficiency step possible and secondly, to to be frank, you are leaving yourself wide open to ridicule making assertions that solar hot water has the fastest payback of any renewable or that a 12 year payback is achieveable.

I'll leave the last word to you:

quentingargan wrote: »

The Gods honest truth is that you cannot come up with a simple formula for payback time. You can use software models from Tsol or Retscreen to calculate this, based on geographical location, amount of water used, size of panel, storage capacity and storage losses etc. You will get a different result for every single household.

Using daytime electricity as the reference point in this calculation invites ridicule from the nay-sayers.

The truth is that there are hidden costs to using fossil fuels - climate change being the main one - albeit that this is disputed by David Bellamy and others.

quentingargan

Clearly gizmo and I have our differeing opinions, and there is a risk of people yawning their way off this page if we just ding-dong, so I won't post here anymore unless and until there are other contributors.

You are quoting me out of context on the day-time electricity. That was in response to a poster who was suggesting that 100% of the solar would be displacing daytime electricity. I already said that "some of the time the energy displaced may be oil or gas at a lower price" and pointed out that the example was a modest system (which is more expensive per watt than larger ones) and that there are other efficiencies as a result of changing the cylinder etc., all of which contribute to the payback.

Essentially, installing solar is a fixed one-off cost which usually includes chucking out a very inefficient cylinder, but after that running costs are close to zero. Pellets and other renewables have ongoing costs which are likely to be indexed to energy prices. I believe energy inflation will be high in the future, just as oil and gas prices have inflated because of impending shortages in supply.

But it is also true that I first got interested in both solar and wind, not because of any economic advantage, but because of an imperative to reduce our carbon emissions and energy dependence. There is a certain satisfaction to be gained in having showers and baths from a totally renewable source that has other values besides monetary ones.

I disagree about the building codes - if you look at self-built houses, many of these opted for far better standards of insulation and incorporated renewables long before the regs kicked in. The regs were needed because right up to last year, developers still were buidling houses using hollow blocks and would never change from that as long as they had the suckers to buy them.

bertie1

If you went to the ESB website & check out the charges most houses ( if they ring the ESB ) with their current consumption & bills will be advised not put in a dual tarrif meter as their current electricity use does not warrent it & the payback is not there .
In order for dual tarrif to pay washing machine , diswashers, dryers & waterheating need to come on after midnight to avail of the cheaper tarrif.

Most people are not disciplined to this. Personally I do not want to switch these appliances on at that hour of the night & have them running while I am in bed. ( A washing machine at high spin will wake the whole house at 1.30 in the morning. )

Washing machines & dishwashers can leak , tumble dryers can catch fire. I would rather be up & about the house while these appliances are running . I do not want to come into the kitchen in the morning to find the whole place under water. ( It has happenend before where the solenoid valve on the water intake did not close properly on the washing machine & I found a flooded garage the following morning . )

The newer more efficient washing machines now have microprocessor controllers on them which means that you cannot operate them on a clock ( like the old ones). Because they are so effecient with their water consumption a wash on an older machine that used to take 1.5 hours now takes 3 hours for the same wash. If you loose power to them you have to manually restart them.

If you ring the esb you will be advised not to change over as the increased standing charge will not make it viable unless you already have storage heating or some other large load that will pay.

gizmo555

bertie1 wrote: »

In order for dual tarrif to pay washing machine , diswashers, dryers & waterheating need to come on after midnight to avail of the cheaper tarrif.

Most people are not disciplined to this.

There's not much discipline to it, it's just an extra button press when filling the machine.

bertie1 wrote: »

( A washing machine at high spin will wake the whole house at 1.30 in the morning. )

Not in my experience, of course, yours may be different.

bertie1 wrote: »

Washing machines & dishwashers can leak , tumble dryers can catch fire. I would rather be up & about the house while these appliances are running . I do not want to come into the kitchen in the morning to find the whole place under water.

Night rate or not, most people routinely run these appliances at night or while they're out at work, etc.

bertie1 wrote: »

The newer more efficient washing machines now have microprocessor controllers on them which means that you cannot operate them on a clock ( like the old ones).

These are exactly the ones which are more likely to have the start delay function built in and the main purpose of it is to facilitate the use of night rate electricity.

bertie1 wrote: »

If you ring the esb you will be advised not to change over

When I rang the ESB I was given the very sensible advice to take daily readings morning and evening for a week or two to get a handle on whether the switch would save money.

bertie1 wrote: »

the increased standing charge will not make it viable

To be clear, I'm not necessarily advising that everyone should get a night rate meter. To break even, you would need to use 1.6 night rate units per day to save the extra standing charges, plus another 1 night rate unit for every 6.8 day units consumed. Some people will find this easier than others. If you're not using electricity for cooking, it should be very easy. Even if you are, I know from direct personal experience it is do-able. In particular, someone who uses the amount of standard rate electricity for water heating that Quentin gave in his illustration would definitely save money.

bertie1 wrote: »

unless you already have storage heating or some other large load that will pay.

Like heating a tankful of water overnight?

quentingargan

By the way, I fill our washing machine by hand with hot water from the tap using a hose (from our solar heater of course). This way, the machine only uses a small amount of electricity for the motor. I do this during the day mostly, or occasionally last thing at night, but our situation is different as we use an old wind turbine / battery combo for our electricity (on which the payback time is measured in millenia....)

bamboozle

gizmo555 wrote: »

I really don't see how. And as someone else - sinnerboy I think - has often pointed out here, there's a reason why domestic-scale renewables are compulsory in the latest building regs. If they made reasonable economic sense, there would be no need for compulsion. That said, I accept there is more to it than pure economics and presumably Joey, like me, wants to leave a habitable world for his children and grandchildren. I'm also not saying no-one should install solar hot water. I just think, firstly they should make sure they have taken every other energy efficiency step possible and secondly, to to be frank, you are leaving yourself wide open to ridicule making assertions that solar hot water has the fastest payback of any renewable or that a 12 year payback is achieveable.

I'll leave the last word to you:

i find you are being overly dismissive of Quentin's comments, i dont think he's trying to pull the wool over anyone's eyes. A major reason why these renewable systems are being made compulsory is that the initial cost is quite high and might if not compulsive prove a deterrant to people to choose them. Finally as quentin suggested there are lower hanging fruit to be considered prior to choosing for solar or any other renewable for that matter.

As a matter of interest what renewable system do you consider to have the quickest payback?

Naux

quentingargan wrote: »

By the way, I fill our washing machine by hand with hot water from the tap using a hose (from our solar heater of course). This way, the machine only uses a small amount of electricity for the motor. I do this during the day mostly, or occasionally last thing at night, but our situation is different as we use an old wind turbine / battery combo for our electricity (on which the payback time is measured in millenia....)

I know that specialised hot water fill washing machines/dishwashers are available in a commercial/industrial setting.

Quentan, I'm assuming you are improvising with a standard washing machine?

Anyone know if they are on the domestic market yet?

bertie1

gizmo555 wrote: »

There's not much discipline to it, it's just an extra button press when filling the machine.

If you are still up after midnight, but for those of us who have to commute & leave by 6.30am , staying up all night to wait to put on the washing , machine, dryer & dishwasher is a non runner. A timer will not work on my fairly new washing machine as the loss of power stops it starting up. Thirdly if I am to get up before 6.00 am I certainly do not want a washing machine heading into a 1200 rpm spin & waking me at 2.30am ( on it way to end the three hour wash that used to take 1.5hours max on the old machine)

gizmo555

bamboozle wrote: »

i find you are being overly dismissive of Quentin's comments, i dont think he's trying to pull the wool over anyone's eyes.

I don't want to personalise the debate, but frankly I think a lot of what he's written in this thread simply doesn't stand up to the least scrutiny.

For example:

quentingargan wrote: »

Changing the cylinder in many houses is not much less than half the price of the complete system as you won't get any grant for this bit. So while it halves the cost of the hot water you are replacing, it also halves the cost of the installation.

The system price Quentin used was €3,400 after the grant. He says here that half of it isn't really attributable to the solar system, because the cylinder should be changed anyway, at a cost of €1,700. You can get a lagging jacket for less than €20. I would be fascinated to see Quentin's calculations justifying either on economic or environmental grounds the expenditure of the other €1,680.

bamboozle wrote: »

As a matter of interest what renewable system do you consider to have the quickest payback?

I don't know, but Quentin made an unqualified claim that solar hot water has the quickest payback, so it's up to him to justify it. He also made a claim that in the best case it's possible to recover the cost of a typical solar hot water system in 12 years. When pressed on this, it transpired the scenario required completely artificial assumptions. In reality, no credible payback calculations I have seen at current energy prices come in anywhere near 12 years, and they anyway require extrapolation of household hot water consumption figures beyond the point where they still make any sense.

My own take on this is that the focus on the likes of solar hot water is tinkering around the edges. What we need to be doing is reducing energy demand, not coming up with expensive technological fixes to salve our consciences.

gizmo555

bertie1 wrote: »

gizmo555 wrote: »

There's not much discipline to it, it's just an extra button press when filling the machine.

If you are still up after midnight, but for those of us who have to commute & leave by 6.30am , staying up all night to wait to put on the washing , machine, dryer & dishwasher is a non runner. A timer will not work on my fairly new washing machine as the loss of power stops it starting up. Thirdly if I am to get up before 6.00 am I certainly do not want a washing machine heading into a 1200 rpm spin & waking me at 2.30am ( on it way to end the three hour wash that used to take 1.5hours max on the old machine)

The point of the start delay function is that you don't have to stay up all night to put on the washing. If you personally don't want the washing machine on while you're in bed, fair enough.

bamboozle

gizmo555 wrote: »

My own take on this is that the focus on the likes of solar hot water is tinkering around the edges. What we need to be doing is reducing energy demand, not coming up with expensive technological fixes to salve our consciences.

well if that's your take then you'll probably agree with Quentin's initial comments on this thread that there are lower hanging fruit such as insulation etc to be considered before solar?

quentingargan

Naux wrote: »

I know that specialised hot water fill washing machines/dishwashers are available in a commercial/industrial setting.

Quentan, I'm assuming you are improvising with a standard washing machine?

Anyone know if they are on the domestic market yet?

Yes, I am improvising. We bought a Zanussi machine with a hot and cold feed, but how it uses these is pretty useless - it assumes that the water is going to be too hot and run all your colours, so for a 40 degree wash, it uses cold feed only, and for a 60 degree wash, it uses both hot and cold. Add to that the fact that the first few litres through the system are cold water already in the pipes, and the nett effect is near zero.

So we just use a hose from the utility room tap and fill the machine through the detergent drawer. I know thats a bit Heath Robinson for most, but why use electricity when we have a cylinder full of hot water?:)

quentingargan

gizmo555 wrote: »

You can get a lagging jacket for less than €20. I would be fascinated to see Quentin's calculations justifying either on economic or environmental grounds the expenditure of the other €1,680.

According to the CIBSE, even a cylinder with its top insulated to BS1566 along with 3 dome fittings and 5 sidewall fittings will lose 184 watts. That's why people call it a hotpress.

0.184Kw X 24 X 365 = 1611 KwHr per year. Say half from electricity at 16c and half from oil at 8c = €193 per year. Payback time 8.68 years.

I haven't looked closely, but I find it hard to imagine that losses from a cylinder with a lagging jacket would be less than a foamed cylinder to BS1566. A good installer should insulate all tank connectors, elbows, vent pipes etc., to get this heat loss to a minimum.

gizmo555

quentingargan wrote: »

According to the CIBSE, even a cylinder with its top insulated to BS1566 along with 3 dome fittings and 5 sidewall fittings will lose 184 watts. That's why people call it a hotpress.

0.184Kw X 24 X 365 = 1611 KwHr per year. Say half from electricity at 16c and half from oil at 8c = €193 per year. Payback time 8.68 years.

I haven't looked closely, but I find it hard to imagine that losses from a cylinder with a lagging jacket would be less than a foamed cylinder to BS1566. A good installer should insulate all tank connectors, elbows, vent pipes etc., to get this heat loss to a minimum.

I'm sorry Quentin, but once again I find your figures are seriously flawed.

First of all, it assumes there is always water in the tank at a temperature differential to the surroundings great enough to create the 184 watt heat loss, 24 x 7, 365 days a year. That certainly doesn't apply to me.

Secondly, heat loss from the tank during the heating season is not a cost - it contributes to heating the house. There goes a minimum of one third and up to a half of your kWh hours "saved", at the 8c/kWh rate for oil. Your savings are now at most €150 and possibly as little as €130.

Next, 1,611 kWh p.a. equals 4.4 kWh per day. I use an electric shower and outside the heating season I have an 3kW immersion on for half an hour in the morning and half an hour in the afternoon for any handwashing, dishwashing etc. Apart from the very occasional bath, that's 3kWh per day. How could I be losing 1.4kWh more energy from my cylinder than I'm putting into it? Even if I assume I lose half of it, it still only comes to a cost of 240 days x 1.5 kWh x 14.4c (Bord Gais supply my electricity!) Total: €51.84. Payback time: 32.5 years :eek:

The false premise in your calculations is that there must be a tankful of piping hot water available 24x7.

Now, you may argue I should change the electric shower for one fed from a solar powered tank, but at the very most we use 1.5kWh per day - that's a further annual cost of less than €80. And as I said previously, the great merit of these showers even though they may not necessarily use renewable energy, they use only the exact amount required and as it's heated at the point of use, there is no heat loss at all. The same goes for dishwashers and clothes washers with cold water feeds.

PS, is the replacement cylinder you would be proposing so efficient that there's no heat loss at all from it?

gizmo555

bamboozle wrote: »

well if that's your take then you'll probably agree with Quentin's initial comments on this thread that there are lower hanging fruit such as insulation etc to be considered before solar?

101%!

gizmo555 wrote: »

I fully accept that energy prices will rise, probably very substantially, over the coming years. But it stands to reason that energy efficiency measures which have the shortest payback periods now will continue to do so as prices rise, and that savings made are generally speaking in proportion to the fossil fuel use displaced. On this basis it seems clear to me that solar hot water systems come very low down the order of priorities. It is amazing, for example, that the "Warmer Homes Scheme" intended to pay for energy saving measures in low income households is only available on a pilot basis in certain parts of the country at the same time that solar HW systems are being grant aided by up to €1,800 nationwide.

quentingargan

gizmo555 wrote: »

I have an 3kW immersion on for half an hour in the morning and half an hour in the afternoon for any handwashing, dishwashing etc. Apart from the very occasional bath, that's 3kWh per day. How could I be losing 1.4kWh more energy from my cylinder than I'm putting into it?

The false premise in your calculations is that there must be a tankful of piping hot water available 24x7.

You are rightly conservative in how you use hot water, but the truth is that the vast majority of houses, rightly or wrongly, have hot running water pretty much all day. They do keep a tankfull of hot water. The calculations from CIBSE are based on cylinder at 60 degrees on top and 40 degrees below.

General norms are that the average consumption of hot water is 40L per person per day of water at 60 degrees.

In relation to your immersion running for an hour a day, assuming that 1 joule = 1 watt per second and it takes about 4.2 joules to heat a gramme of water by 1 degree.

Your 3Kwhr per day is 3000*3600 joules, divided by 4,200 gives 2571 litre degrees. Assuming incoming temp of 12 degrees and outgoing 60, thats 2571/48 litres, or 53L. And that is assuming no heat losses in the cylinder in-between heat ups, which is unlikely.

So your requirements are modest and I would honestly not suggest that solar is for you if I was asked to assess your needs. That regularly happens by the way, but more often with wind where I regularly recommend against a wind turbines on a site because it isn't viable, while others are promising 5 year paybacks.

gizmo555

quentingargan wrote: »

You are rightly conservative in how you use hot water, but the truth is that the vast majority of houses, rightly or wrongly, have hot running water pretty much all day. They do keep a tankfull of hot water.

I'm not conservative or parsimonious in my hot water use, I just don't waste money and energy heating far more than I or my family could possibly use.

What is the source for your information that "the vast majority of houses" do maintain a tankful of hot water at 60 degrees night and day, all year round? I certainly don't know anyone who does. Only someone who has no understanding of energy use and its impact on their bills would be mad enough to do so. Even if you're right, the solution is not a €1,700 cylinder to enable the same profligate waste to be done cheaper, but understanding and taking better control of one's energy use. The SEI is addressing this issue now with the €500 grant for heating controls available through the Home Energy Savings scheme. Even a simple timer on the immersion controls would eliminate most of this waste.

quentingargan wrote: »

I regularly recommend against a wind turbines on a site because it isn't viable, while others are promising 5 year paybacks.

I would suggest that claiming a possible sub-9 year payback on a €1,700 hot water cylinder is in the same realms.

I note also you haven't addressed the points that heat loss from the hot water cylinder in the heating season is not a cost and the fact that your payback calculations implicitly assume that there is zero heat loss from your proposed replacement cylinder.

fergus.wheatley

A 6m2 collector area and a 300 litre storage solar installation will produce about 2000 kWh of energy in a year. Replacing an un-insulated cylinder with a high efficiency correctly installed cylinder will save towards another 2000 kWh. The total annual savings of 4000 kWh would require the equivalent of about 500 litres of oil per annum, if a heating system efficiency of 75% is assumed.

The payback can then be thought of in terms of the amortised cost of this oil over a number of years, assuming a particular inflation rate. Energy inflation and thus future energy prices are very difficult to estimate, so an easier way to grasp the potential savings, is to imagine that you are effectively buying 500 litres of oil per year, for the life time of the solar installation and assess this against the initial capital cost.

Poor Uncle Tom

Solarbook.ie wrote: »

A 6m2 collector area and a 300 litre storage solar installation will produce about 2000 kWh of energy in a year. Replacing an un-insulated cylinder with a high efficiency correctly installed cylinder will save towards another 2000 kWh. The total annual savings of 4000 kWh would require the equivalent of about 500 litres of oil per annum, if a heating system efficiency of 75% is assumed.

The payback can then be thought of in terms of the amortised cost of this oil over a number of years, assuming a particular inflation rate. Energy inflation and thus future energy prices are very difficult to estimate, so an easier way to grasp the potential savings, is to imagine that you are effectively buying 500 litres of oil per year, for the life time of the solar installation and assess this against the initial capital cost.

Your 500 litres of oil/year is worked on the assumption of an existing UNINSULATED cylinder.

Any existing heating systems containing an uninsulated cylinder must be nearing the end of their lifespan at this stage anyway. The average system needing upgrading will not include an uninsulated cylinder.

If you are going to put a model out there, please make it realistic.

Joey the lips

Poor Uncle Tom wrote: »

If you are going to put a model out there, please make it realistic.

This is my problem with the solar panel industry... Its easy to play with figures....

Poor Uncle Tom

Joey the lips wrote: »

This is my problem with the solar panel industry... Its easy to play with figures....

The more I read up on these systems the more I find myself bogged down in oceans of dross. If I'm trying to choose a system which is best for my needs I would like to be able to compare like for like. The bales of litrature out there on the different systems makes that impossible. There are so many different component makers out there that they put a different spin on their own item to make it shine the brightest.

Is there any handbook, from someone who has done some comparison testing. I know the IAB or BBA Certification is usually our barometer in such cases, but, most of the components I've checked up on do not have these Certifications.

One thing that constantly springs to mind regarding these systems is the amount of different parts associated with each and the potential for parts to fail. What is the lifespan of a good solar system? what component is the most expensive? what is the next expensive component? and so on.. what regular maintanance/servicing will a system need?

Joey the lips

Poor Uncle Tom wrote: »

The more I read up on these systems the more I find myself bogged down in oceans of dross. If I'm trying to choose a system which is best for my needs I would like to be able to compare like for like. The bales of litrature out there on the different systems makes that impossible. There are so many different component makers out there that they put a different spin on their own item to make it shine the brightest.

Is there any handbook, from someone who has done some comparison testing. I know the IAB or BBA Certification is usually our barometer in such cases, but, most of the components I've checked up on do not have these Certifications.

One thing that constantly springs to mind regarding these systems is the amount of different parts associated with each and the potential for parts to fail. What is the lifespan of a good solar system? what component is the most expensive? what is the next expensive component? and so on.. what regular maintanance/servicing will a system need?

Everyone has that problem. I use to liken the confusion to the "emporers new clothes" you dont quite know what your getting. I also think the dept of environment is wrong to feel that because builders put panels on houses they are contributing to co2 reduction. Think of the early 90's when the councils start installing a massive amount of weatherglazed windows into council houses. It was later felt a lot more would have been acieved by simply upgrading the roof insulation.

There is no standard in solar panels. There is actually poor standards in radiators.... With increasing house insulation smaller radiators can actually be specified but plumbers are over specing for fear.

I think the same is happening with panels. except for they are over estimateing returns. It all boils back to the old reliable... If its too good to be true it usually is..... I see every house in Spain has solar panels for there hot water.:rolleyes: I wonder why.....?

muffler

My great grandfather actually pioneered a "natural heating system" a long time ago.

Joey the lips

muffler wrote: »

My great grandfather actually pioneered a "natural heating system" a long time ago.

Now here's me thinking your talkin about a good owl ride and off course you have to bring drink into it...

heinbloed

The Estif organisation has now a list of certified ST SYSTEMS as well, not only collectors.
See
http://www.estif.org/solarkeymark/regsys.php

These systems include everything, from collector to storage tank.
All that the installer has to figure out is the energy demand which has to be suplied.

fergus.wheatley

Nearly every single system that I come across has an uninsulated cylinder installed. Typically about 40% of the cost of installing a solar system consists of changing the cylinder. At the end of the day, installing a solar system saves money and CO2 emissions, it's just half the savings come from the "unsexy" side of things by making hot water storage more efficient.

Regardless of energy prices, the following benefits exist;

1. More hot water is available during the summer.
2. Better energy rating for the dwelling and higher house value
3. Lower CO2 emissions
4. Fuel cost savings of up to 25%.

fergus.wheatley

Joey the lips wrote: »

Hi Folks,

Have been considering going solar as an investment. I am not loaded but consider it like a retirement plan anything invested now will repay when I am retireing.

Any way, My house front is south south East faceing and my back north north west faceing. I also have a gable taking up half of the front.

What is my options for solar? I half know the answer but would appreciate all opinions. Thanks

I have attached expected outputs for 40 and 60 vacuum tubes for a variety of roof angles and orientations. In summer there is little enough difference, but in winter the more south facing the better.

Poor Uncle Tom

Solarbook.ie wrote: »

Nearly every single system that I come across has an uninsulated cylinder installed.

So you are saying that nearly every single system that you have come across in the last, say 2 years, has had an uninsulated cylinder installed!!!!!

I don't think so.

fergus.wheatley

Poor Uncle Tom wrote: »

So you are saying that nearly every single system that you have come across in the last, say 2 years, has had an uninsulated cylinder installed!!!!!

I don't think so.

Nearly all my work in in the retrofit market. I can only talk about my own experience, but the last 6 installs I worked on had uninsulated cylinders.

Joey the lips

Solarbook.ie wrote: »

Nearly all my work in in the retrofit market. I can only talk about my own experience, but the last 6 installs I worked on had uninsulated cylinders.

Well that can actually be an indicator of the market. When you consider there was the guts of 60000 houses built a year during the good times


http://www.breakingnews.ie/ireland/kfkfojgbauoj/


I estimate we have at least 4 years at 60000 that 240 000 houses. If most of the houses you worked on were uninsulated then I suspect they are old housing stock. There is no way IMO the vast majority of buyers(1st time buyers) were buying into solar if the cylinders were uninsulated meaning that the majority of buyers are actually the older age bracket which enforces my thoughts on my "emporers new clothes" theory....ie they are buying into perceived savings.

What do you think

Poor Uncle Tom

@Solarbook.ie

Without getting into a tit-for-tat arguement my point is that you threw a saving figure out there of 500 litres of oil per year, based on asumptions.

If I am going to build a new house and I am considering installing an oil boiler for my primary source of heating and I read your post my first asumption is that if I install a solar panel heating system I will save the equivolent of 500 litres of oil per year.

This is not the case as any new house will not install an un-insulated cylinder as part of their system, this reduces your assumed savings by 50% straight away. You also neglect to mention that the oil boiler will also have to kick in to suppliment the solar heating for a large portion of the Autumn, Winter and Spring which reduces further your purported savings.

What I am saying is I would like someone to give me the facts straight and I feel you are not doing that.

gizmo555

There is an ongoing theme among many of the posters in this forum who are in the business of installing solar hot water systems of citing potential savings for their systems which on examination are based on the most inefficient possible existing systems and solar energy substituting for the most expensive possible energy sources.

Many of the so-called "savings" could be obtained at a lot less cost and hassle by, for example, spending €25 on a lagging jacket, or getting a night rate electricity meter installed by ESB Networks at no cost.

Simple changes of habit can make big differences too - if, for example, you usually spend five minutes in the shower, reducing this by one minute will yield an instant 20% saving of both energy and water.

As for such a system adding to the value of a house, I would be sceptical. Like so many other house "improvements", if done well it may act as a selling point, potentially making the house easier to sell, but of doubtful value in actually increasing the price obtained. If done badly, it may actually reduce the house price. For example, many people find tube solar collectors ugly and they could easily put off potential buyers.

I always recall when looking at claims of adding "value" to houses a survey of UK-based estate agents published by the Sunday Times a couple of years ago - I'll try to find a link later. The bottom line was that the only improvement which could reliably add at least as much as it cost to a house's value was painting and decorating. None of the dozen or so others examined (extensions, patios, etc) could be relied on to even recover their cost, and many actually reduced house values by putting off potential buyers.

quentingargan

Joey the lips wrote: »

Well that can actually be an indicator of the market. When you consider there was the guts of 60000 houses built a year during the good times

The majority of retrofits I have seen have also been to houses that relied largely on laundry to keep the cylinder warm! That part of the house is traditionally called a hotpress for very good reason!

Even where the cylinder has been lagged, or insulated with a few mm of foam, the fittings coming from the cylinder, and associated pipework has always been warm as toast. There are massive losses in most hotpresses, and it is true that a fair share of the cost of installing solar water heating is replacing the cylinder, re-fitting the pipework, and insulating everything properly afterwards.

Eh, I have seen completed solar projects, including photos on boards, where the end results were still unsatisfactory....

You might argue that this is heat just lost to the house, but during the summertime, this isn't the case. And a lot of it lost through gaping holes in the hotpress ceiling where heat just goes into the attic.

gizmo555

With respect, Quentin, this is yet another variation on the same theme. If there are serious deficiencies in cylinder and pipework insulation, or gaping holes in hotpress ceilings, these are issues which can be easily resolved as a DIY project and at a fraction of the typical €2,500 to €3,500 after grant cost of a solar retrofit.

TBH, you and Solarbook come across like the proverbial man with a hammer to whom every problem appears to be a nail. There are pros and cons to solar hot water systems, but fixing holes in ceilings and bringing insulation up to a reasonable standard can't reasonably be counted among the pros.

quentingargan

gizmo555 wrote: »

If there are serious deficiencies in cylinder and pipework insulation, or gaping holes in hotpress ceilings, these are issues which can be easily resolved as a DIY project

Agreed. I would be the first to tell people to look at all the low-hanging fruit first. I've often said to people not to look at solar until after they have done the attic, draught proofing etc.

But there is an added value to having a well insulated cylinder to replace the usual jumble of clothes tossed over the copper cylinder. It contributes to the savings made, but only if other aspects of the project also stack up for you.

heinbloed

Poor Uncle Tom wrote: »

What is the lifespan of a good solar system?

The sellers of ST systems who also do the installation give - on the EU continent- a lifetime of over 20 years as a number to take. So do the civil engineers/heating engineers over there who have to sign for the energy suply of a building. This is not to be mixed up with the guarantee, this could be anywhere between 2-20 years, depending on the seller and his conditions (maintenance!).

In France for example any installation being part of a domestic structure - and this includes the heating and water system- cares a legal guarantee of 10 years. Be it a water tap or a radiator, a boiler or a shower tray, a sewer or a ST system.
This French guarantee is however nilified if the owner neglected his duties (maintenance!).

Poor Uncle Tom wrote: »

... what component is the most expensive?

This depends on the system. Technically underdeveloped installations must be maintained on a regular base. The call for the plumber and his work every two years costs more primary energy than would be saved - with toy installations. The annual or bi-annual maintenance is the most expensive component during the life span of such a system.

What leads to the next question:

Poor Uncle Tom wrote: »

....what is the next expensive component?

The collector. If something goes wrong with these technically underdeveloped systems it is usually the collector which has to be replaced.
Looking at standard collectors freezing or clogging or fogging-up the replacement of it costs something between € 500-800 including all costs in Ireland. Cowboys do it cheaper, dumping the left-overs in the field, draining glycol into water systems etc., using no proper safety equipment when working on roofs.
Cost of the standard 2m2 flat collector when imported: € 150-200 .- .....

So to reduce costs to a contemporary €0.03 per kWh modern ST systems are no toy installations. Nor are their installers fellows who depend on FAS schemes or other subsidies, ST energy is fully marketable to it's real costs.
In Denmark installers of new ST systems charged € 0.045 per kWh in 2006, nowadays it is down to € 0.03 per kWh when newly installed....metered and individually billed to the consumer.

You forgive me not to publish a link to these relevant economic numbers and to those who offer them.
It would be against the rules.....

Your questions are justified. Similar to the question what does a car cost. What is it's most expensive part, the next one, how long does it last.....

gizmo555

quentingargan wrote: »

Agreed. I would be the first to tell people to look at all the low-hanging fruit first.

All other fruit hangs lower.

quentingargan wrote: »

But there is an added value to having a well insulated cylinder to replace the usual jumble of clothes tossed over the copper cylinder. It contributes to the savings made, but only if other aspects of the project also stack up for you.

One can get a very well insulated cylinder for about €500 without going to the trouble of putting in a solar system. You can get a lagging jacket for €25. Anyone who is relying on a "jumble of clothes" to insulate their hot water cylinder by definition falls into the category of people who you "would be the first to tell . . . to look at all the low-hanging fruit first."

Poor Uncle Tom

heinbloed wrote: »

Your questions are justified. Similar to the question what does a car cost. What is it's most expensive part, the next one, how long does it last.....

Thank you for answering them.

(please quote a post within tags, it's monotenous following you around doing it...thanks)

fergus.wheatley

I was collecting a 300 litre triple coil copper cylinder yesterday from DPL in Kilmainham, the lads hadn't brought it down to the shop so they sent me to the factory at the back where I had a chat with Brian, the foreman. 40% of the cylinders he sends out TODAY are UNINSULATED.

gizmo555

fergus.wheatley wrote: »

40% of the cylinders he sends out TODAY are UNINSULATED.

This is plain daft, but adhering to the "low hanging fruit" principle, it doesn't show that the buyers of these cylinders need full-blown solar h/w systems, merely that they should have bought an insulated cylinder instead. If we can have laws brought in to take incandescent light bulbs off the market, why are these still still even allowed to be sold?

heinbloed

The building regulations stipulate energy efficient building methods already.
That there is little demand from those who foot the energy bills to get value for money is due to the undereducation of the broad masses.
Here the state is organising the consumer organisation, in other countries it is the consumer who organises the state.
As long as there is no demand for energy efficiency from the consumer side there won't be any.
If the state forces by law energy saving in the home the money spend to do so (be it for the purchase of building services or materials) will be spend - on the energy to provide for these things.
Only a reduction on spending power will lead to energy savings.

But why saving energy in the first place? The sun shines for free....