Is solar worth the investment?

Jane98

Hi,

I am about to embark on a major renovation and extension project of a detached house.

Our budget is very tight and tender quotes have come in over our budget so need to look at getting it down to budget so one of the things I am looking at is the solar which is costing €5,500.

We are a family of 6 and will be using gas central heating overwise to heat the water? Any advice to help me make a decision?

Calahonda52

I don't believe it is worth it, in part because, as in your case, the system is sized to meet the current needs based on occupancy.

There wont always be 6 and you are still stuck with this kit.

You can manage the hot water usage in other ways.
Put aerators on all taps and showers.
If water is hard look at softener.
Consider a boiler that heats water on demand only and so no immersion.
Downside is that the teenagers can stay in forever, until the gas runs out

However the way around that is a time limit on the shower, kit I use can be set for say 20 minutes in any two hour period.

MicktheMan

Solar thermal make sense in very few situations and yours isn't one of them.

It looks like you will be installing a very efficient water heating system (gas) anyway so why spend more on a second water heating system? Or to put it another way; how many people buy an electric car when they already have a perfectly good car and are tight for cash?

Markcheese

I have solar water heating,and I like it- but it was an inexpensive flat plate system that my dad and I installed - if I'd had to pay full whack there's no way it'd pay -
That said pipe is cheap - so run a flow and return pipe from your attic to the hot press -(and a wire or 2 for sensors ) make sure that there's a power supply to your hot-press (so you can run your pump,) and leave it at that - you can retrofit it all later if you want -

freddyuk

Calahonda52 wrote: »

I don't believe it is worth it, in part because, as in your case, the system is sized to meet the current needs based on occupancy.

There wont always be 6 and you are still stuck with this kit.

In addition, the most common ones used here in ireland require a refrigeration engineer to service them, more expensive than the annual gas boiler service.
Unquote:

How come? Solar thermal uses free solar energy with a tiny circulating pump whereas "the most common ones used here in Ireland......" are in fact heat pumps which need power 100% of the time and then multiply that input power to varying degrees to heat water.The solar input is pretty academic as they work in wind, snow rain and at night.
As we do not know what kit the OP has been quoted for with €5500 worth of solar it is impossible to make an informed point?
Solar either heats water to a useable temperature directly or it preheats water thus giving the boiler or other heat source a lower temperature rise thus saving oil/gas/electric throughout the year.
If the system becomes over specified as the load decreases (less people) then the system becomes more effective for a longer period through the year without any additional capacity. Even less for the back up system to do. Lower energy bills.

therealmccoy

A solar water heating solution isn't JUST an option to save money. It is an option to Save Money (or cover the cost of itself over lifespan), Have a System which is kinder to our environment but also a convenience item of having hot water on demand. A lot will depend on the lifestyle of the homeowner and users of the system and how much they care about their carbon footprint.

Personally, I am a huge advocate of Thermodynamic 'Solar' as it works all year round as opposed to being limited to summer months from Traditional Solar. Yes, it a glorified Air-to Water Heat Pump. But on a high usage based system as suggested, it would have a payback period of less than 10 years for a system which is Greener and will always give you a constant supply of Hot Water. Systems can be installed with a new cylinder for circa €4995.

Jane98 wrote: »

Hi,

I am about to embark on a major renovation and extension project of a detached house.

Our budget is very tight and tender quotes have come in over our budget so need to look at getting it down to budget so one of the things I am looking at is the solar which is costing €5,500.

We are a family of 6 and will be using gas central heating overwise to heat the water? Any advice to help me make a decision?

Wearb

therealmccoy wrote: »

A solar water heating solution isn't JUST an option to save money. It is an option to Save Money (or cover the cost of itself over lifespan), Have a System which is kinder to our environment but also a convenience item of having hot water on demand. A lot will depend on the lifestyle of the homeowner and users of the system and how much they care about their carbon footprint.

Personally, I am a huge advocate of Thermodynamic 'Solar' as it works all year round as opposed to being limited to summer months from Traditional Solar. Yes, it a glorified Air-to Water Heat Pump. But on a high usage based system as suggested, it would have a payback period of less than 10 years for a system which is Greener and will always give you a constant supply of Hot Water. Systems can be installed with a new cylinder for circa €4995.

I don't know how you can say less than 10 year payback. Installation alone nearly €5000. A payback period on that alone (not including maintenance) would be assuming that current domestic water heating is costing €500 per year.
I think that the only reason either of these systems are installed is to meet building regs. They rarely make economic sense.
As for carbon footprint, wood burning stoves or pellet boilers would get you around that.
Not having a go at you, but I have seen too much money wasted in these, especially in retro fit.

youtheman

If money is tight, I'd just go ahead and install the twin coil cylinder and the thermostatic mixer valve for now. You can add the rest later (that's how I did it, in 2 phases).

therealmccoy

On high usage based systems, someone can save up to €700 per year based on an alternative heating Water alone. (Immersion, Oil/Gas). Assuming that figure is a bit on the high side, to be conservative a saving of around €500 per year is sound. If a system costs €5000 to put in and gives an annual saving of €500 then it has a 10 year payback period. There is no annual maintenance with these systems once installed and commissioned correctly.

To be completely overkill, let's say they have an annual saving of €250 (which is severely low) and the system costs €5000, with a lifespan of 20 years, the system pays for itself. As I said in my original comment, this product isn't just beneficial on monetary basis. Look at the reduced carbon footprint it has compared to Oil/Gas and also appreciate the convenience factor.

Wearb wrote: »

I don't know how you can say less than 10 year payback. Installation alone nearly €5000. A payback period on that alone (not including maintenance) would be assuming that current domestic water heating is costing €500 per year.
I think that the only reason either of these systems are installed is to meet building regs. They rarely make economic sense.
As for carbon footprint, wood burning stoves or pellet boilers would get you around that.
Not having a go at you, but I have seen too much money wasted in these, especially in retro fit.

RJF

Hi McCoy, what % of the overall DHW do you expect a thermodynamic solar system to provide? Is there any data available to back this up? What would you consider a high usage based system?

Wearb

therealmccoy wrote: »

On high usage based systems, someone can save up to €700 per year based on an alternative heating Water alone. (Immersion, Oil/Gas). Assuming that figure is a bit on the high side, to be conservative a saving of around €500 per year is sound. If a system costs €5000 to put in and gives an annual saving of €500 then it has a 10 year payback period. There is no annual maintenance with these systems once installed and commissioned correctly.

To be completely overkill, let's say they have an annual saving of €250 (which is severely low) and the system costs €5000, with a lifespan of 20 years, the system pays for itself. As I said in my original comment, this product isn't just beneficial on monetary basis. Look at the reduced carbon footprint it has compared to Oil/Gas and also appreciate the convenience factor.

I don't agree that a figure of €500 per year is sound. That would equate to about half the annual heating bill for gas or oil. Average cost of most customers I have (all oil) is €1000 p/a including heating and domestic hot water.

Anyway anyone reading this thread will now have our alternative view points, which was my main reason for posting.

Calahonda52

A key numbers required here: the daily usage of hot water; the delta T being provided by the SP; the cost of alternative energy to SP.

Lets do some math: Am happy if this is wrong but we do need to have stab at it.

Take the 250 euro annual saving, at 5 c per kWh for gas this is 5,000 kWh pa or 13.74 kWh per day.

Assume hot water daily usage of 250 liters a day, everyday

This is 250 kg of water and lets assume a delta T of 50 ie we need 60 and it comes in at 10 degrees C
so 250 by 50 is 12,500 KgC

The Specific heat capacity of water is 4.186 kJ/KgC
so 52,325 kJ

1 Watt is 1000kJ/s
so (52,325 *1000)/3600 is 14,534 watth or 14.5 kwh which is close enough to the 13.74 for gas

So based on that unless you are lashing through 250 litres of 60 degree water a day, you wont make the 250 saving.

In addition there is the extra cost of serving the SP kit. You are already serving the gas boiler.

Whats wrong with this math?

ted1

therealmccoy wrote: »

On high usage based systems, someone can save up to €700 per year based on an alternative heating Water alone. (Immersion, Oil/Gas). Assuming that figure is a bit on the high side, to be conservative a saving of around €500 per year is sound. If a system costs €5000 to put in and gives an annual saving of €500 then it has a 10 year payback period. There is no annual maintenance with these systems once installed and commissioned correctly.

To be completely overkill, let's say they have an annual saving of €250 (which is severely low) and the system costs €5000, with a lifespan of 20 years, the system pays for itself. As I said in my original comment, this product isn't just beneficial on monetary basis. Look at the reduced carbon footprint it has compared to Oil/Gas and also appreciate the convenience factor.

Your figures are rubbish.
Case 1: if the money to purchase and install the susyem is borrowed 5,500 quickly becomes 7,500.

The 5,500 could be put in a fixed term bond which returns a yield and the gas bill paid as normal.

So the 20 year payback is out the window and your left with a payback that exceeds the life if the unit. What kind of maintenance does the system require that will cost too.

If they care about the enviorment they could use the 5k to change their car to a new efficent one or buy an EV or plant trees and sequestion carbon

MicktheMan

Calahonda52 wrote: »

Whats wrong with this math?

Nothing.

What the salesman is depending on is the fact that most people haven't a clue what they spend on their dhw and can therefore throw out numbers to make their product sell.

Here is my own real data:
5 in household (incl 3 teenage girls!)
DHW supplied solely by conventional oil boiler (winter & summer)
Measured annual spend on dhw <275 euro (@90 cent / litre)

Taking these figures and assuming that 60% of dhw can be supplied by solar, then a saving of 165 euro per year saving by investing 5.5k. This equates to a simple roi of 3% plus money is tied up on the roof.
Also, I don't buy into the carbon footprint argument either; after all these systems need to be manufactured, transported, installed, maintained, dumped/recycled etc when there is already a perfectly good water heating appliance installed and paid for.

Capt'n Midnight

therealmccoy wrote: »

To be completely overkill, let's say they have an annual saving of €250 (which is severely low) and the system costs €5000, with a lifespan of 20 years, the system pays for itself.

Only if there is no time value for money.

At present a 10 year mortgage is 4.99% give or take
5% over 20 years works out at
Total Monthly Payment: €33.00
Monthly Payments: 240
Total Interest: €2,920.00
Total Credit: €7,920.00

€33 per month is €396 a year. ( for 4% it's €363.60 a year. )

So you'd need to save €400 a year to pay off a €5,000 investment over 20 years if you borrowed the money at current mortgage rates.

You can ignore interest repayments if you have the cash burning a hole in your pocket or you are paying back in a short time and you value the other benefits. But if you are waiting on the savings it's worth considering what else you could get like extra insulation.


Regardless you have to consider investing in something where the break even time may be outside the warranty period.


Of course fuel prices will probably go up. But solar panel prices may also fall. Like the fella said if you could get a twin coil cylinder for future proofing.

Jane98

Any idea how much more the twin coil cylinder would cost over and above the standard cylinder and if there are any negatives to installing it (bar initial cost difference) should I never decide to instal solar?

Wearb

There used to be a guy on here called Shane007. He used some sort of air to water system (ariston, I think) for DHW and seemed to be better value than those solar panels.

Look of some of his old threads on the subject.

Found the link.
http://touch.boards.ie/thread/2057175245/1/#post89608669

renguy

There are systems available to retro fit existing systems from €3,500 from Irish based companies.