Heat Pump Running Costs

dominatinMC

https://www.boards.ie/discussion/comment/121637856#Comment_121637856

Even without context (house size, room temps), that seems like crazy usage. Can you provide some details on the size of your house, BER/airtightness, room temps, flow temps? Plenty of advice on here to get that usage down

dominatinMC

https://www.boards.ie/discussion/comment/121638500#Comment_121638500

Is that electricity usage for 2 months? Although it's high, it's probably not drastically high for a new house(?) drying out.

Nevertheless, I don't think I'd attribute your usage to the DHW. By all means, reduce this to 50 degC, and you will see a difference, as the immersion heater is probably responsible for the heating from 50 degC+. However, what is your flow temp set to? If this is too high (as is often the case when HPs are installed), it would be responsible for large usage.

mitresize5

https://www.boards.ie/discussion/comment/121638563#Comment_121638563

yes - thats the usage for 2 months

its a renovation we're in since August so it has dried out a fair bit

flow temp is 30 now but I did see it at 45 last night when I checked

gandalfio

Change your upstairs stat to 18, and your downstairs to 20 and you'll notice a big difference in your usage/bills. Even with stat at 20, your living room will be warmer than that with people being in it, TV and lights on etc.

dominatinMC

https://www.boards.ie/discussion/comment/121638589#Comment_121638589

Okay, sounds like you're running weather compensation. Which I assume was set by your installer. My guess is that you need to modify your curve to suit your house. That will take some time, but worth it in the long run. 45 degC seems excessively high.

munsterfan2

250sqm new build ( 3years old) with a Waterkotte GSHP. Last few days have been at 15 - 18 kwh per day for heating & 3kwh for dhw. Here is the current heat flow curve - I have it at +1 during the day and a step back of -5 from 23:00 to 02:00 ( cheap rate kicks in ). The great thing about the cold is the solar panels are flying, with 25kwh generated plus the 14kwh usable of the battery I am not seeing too much daytime electricity usage

Room temperature in main living are holds steady, 21.5 - 22

staples7

https://www.boards.ie/discussion/comment/121638715#Comment_121638715

Id agree with this. Changing your hot water from 54 to 50 will be minimal change regards kw used. eg my hot water usage in very busy house is 2.5kwh per day summer and winter

The real damage is being done by the UFH heating. having it set to 22' is a killer. I know its subjective but 20' is comfortable.

on top of the above if you can run at night where its more than half the day rate I think this is the best step in terms of cost saving. Ive ben doing this for 6 years now. averaging yearly heating and hot water below E500 for the year. 2800sqft

keno-daytrader

210sqm 2 story we are using 3kWh for DHW and 11-13 kWh for underfloor in this cold spell per day. UFH flow at 29c , downstairs set to 21.5c A1 house, not quiet passive but not far off. I only use the heat pump in daylight hours.

keno-daytrader

https://www.boards.ie/discussion/comment/121638500#Comment_121638500

Limit the flow temp for your underfloor heating, there is no way the ufh should be run that high (45). You will see a huge difference in your usage, it happened to us also, the installers just set it on "dumb" mode so they dont get callbacks. Try max 35c for now and bring it down bit by bit over a few weeks until it wont keep room temp where you want it anymore, then bump up a degree or 2. Its trial and error for every house, but will so pay off.

Edit, sorry I missed that you had rads upstairs, but the same principal applies, experiment with getting that flow temp as low as you can get away with.

mitresize5

https://www.boards.ie/discussion/comment/121638765#Comment_121638765

thanks for the feedback - when you say modify the curve, what does this mean.

mitresize5

https://www.boards.ie/discussion/comment/121638715#Comment_121638715

Im ok with this, my better half likes it balmy :-)

mitresize5

https://www.boards.ie/discussion/comment/121638838#Comment_121638838

thanks for the feedback

Can you explain the running at night to me. Does this mean going on a day/night rate with the supplier

Do I have to program to pump to call for more heat at night, e.g. get it above desired temp on cheap rate and top up during the day

mitresize5

https://www.boards.ie/discussion/comment/121638936#Comment_121638936

thanks for the feedback,

is the flow temp the temp of the water in the heating system? If its limited is it slower getting to desired stat temp as it doesnt heat the water as high?

I can see why limiting it would reduce the energy usage, just wondering what the draw backs are, if any

graememk

https://www.boards.ie/discussion/comment/121639067#Comment_121639067

The lower the flow temperature the more efficient the heatpump is.

keno-daytrader

https://www.boards.ie/discussion/comment/121639067#Comment_121639067

Yes, the flow temp is the warm water running thru your underfloor and rads. What i meant by limit is the temperature of the water, the lower you can get your flow temp the more efficient your system will be. Heat pumps are meant to deliver a trickle of heat over long sustained periods of time compared to traditional boilers, that use short bursts of on demand heat.

feelings

https://www.boards.ie/discussion/comment/121638515#Comment_121638515

new build 230sqm, 2 zones, 20.5 downstairs (ufh), 21 upstairs (rads). BER A2   36.8 (kWh/m2/yr). Flow rates... haven't a breeze. Fiujitsu 8kw heat pump. Will have to try get some info from the unit.

dominatinMC

https://www.boards.ie/discussion/comment/121639334#Comment_121639334

In fairness, your room temps don't seem excessive. Check your heat pump inside unit for the flow temp (not flow rate). My guess is that it is set too high - probably high 30s/low 40s.

dominatinMC

https://www.boards.ie/discussion/comment/121638993#Comment_121638993

The weather compensation curve is basically a means for your heat pump to regulate the flow temperature in accordance with the ambient air temperature. So as air temperature drops, the flow temperature increases and vice versa. The values used to generate the curve are often set in some arbitrary manner, and not really specific to the house. So you should look at editing them to suit your needs.

poker--addict

Can anyone recommend a heat engineer?

seem to be few and far between in Ireland !?

andyd12

https://www.boards.ie/discussion/comment/121635222#Comment_121635222

How is heat within each room regulated with no control?

Eleusis

https://www.boards.ie/discussion/comment/121658928#Comment_121658928

You can and still open and close the valves on top of the manifold.If one room is colder then you can open this one a bit more or close the others if they are all fully open already. Take a bit of playing around to balance the house so it's works with one zone.

andyd12

https://www.boards.ie/discussion/comment/121635979#Comment_121635979

For me, who is currently living in a renovated garage/apartment with high levels of insulation but little to no attention paid to air tightness, I have really noticed a difference since it became much more windy yet milder in the past few days. The place feels colder now than last week when it was very cold.

I am building a new house soon and for the above reason will be focusing heavily on air tightness this time.

andyd12

https://www.boards.ie/discussion/comment/121658948#Comment_121658948

Ok thanks so just adjusting the flow rates in each loop?

But is the system not a bit dumb then? For example, if the sun begins to shine into a room, the heating system has no way to notice this solar gain

Eleusis

https://www.boards.ie/discussion/comment/121659056#Comment_121659056

yea it is. i suppose its trade off of having a single zone which heat pumps prefer. HRV is good in this scenario becuase it will equalise the heat around the house and its essential in combination with airtightness

keno-daytrader

https://www.boards.ie/discussion/comment/121659000#Comment_121659000

Great thinking. Go take the airtightness course and try to get as close to passive results as you can, it will pay off so much in your new house.

ColemanY2K

https://www.boards.ie/discussion/comment/121659000#Comment_121659000

if its a self build it would be well worth your time doing a course like this one which was held last week...

https://passivehousesystems.ie/airtightness-installer-training/

i self taught myself but probably should have done the 1 day course myself. the initial test came back with an ACH score of 1.8 which disappointed me as i was looking to achieve 0.6. fortunately a lot of the leaks were in known locations and could be tackled.....so fingers crossed the final air tightness test achieves the target.

newhouse87

https://www.boards.ie/discussion/comment/121658928#Comment_121658928

As mentioned balancing the system regulates. You get to know your own house, flow temps, etc. Back to 29 flow now in theses conditions, 31 in coldest temps.

Cyrus

we have solid hardwood floors (aesthetic rather than practical considerations) which hampers the efficiency of our UFH (need higher flow temps)

newhouse87

https://www.boards.ie/discussion/comment/121660085#Comment_121660085

Yeah my kitchen with tiles warmest. Laminated timber does not conduct near as good and hardwood worss again. Did you remove actuators?

Cyrus

https://www.boards.ie/discussion/comment/121660115#Comment_121660115

no not yet, on the list, i spent last few days trying to figure out why we had no heat (but did have DHW) we had a power cut and the flow rate had dropped below 10 degrees, requires a manual restart! just back working now.

andyd12

https://www.boards.ie/discussion/comment/121659145#Comment_121659145

That is true. Thanks for the info

https://www.boards.ie/discussion/comment/121659474#Comment_121659474

https://www.boards.ie/discussion/comment/121659501#Comment_121659501

Thanks for the comments here. I have contacted them in relation to more upcoming courses. I was going to wing it with Youtube and learn as I go but for 65 quid, the course would be a good head start.

@ColemanY2K you are currently in the middle of the build? For the initial test, you just hired someone to do a blower test?

https://www.boards.ie/discussion/comment/121659940#Comment_121659940

Thanks, good to know moving forward

theintern

https://www.boards.ie/discussion/comment/121638838#Comment_121638838

Can I ask how you're configuring to take max advantage of the night rate?

Are you just running hot water at night, or are you upping stat temperatures at night, and then allowing it to cool down during the day? I'm on a night rate and want to take as much advantage as I can.

To add to the data here, 2023 figures. 134sqm, A2, UFH downstairs, rads upstairs. Downstairs generally set to approx 22. Upstairs to 20.

Heating used - 1554kWh

Water - 806kWh

Total - 2360kWh

Peak last week was 28kWh.

Eleusis

https://www.boards.ie/discussion/comment/121660085#Comment_121660085

Im not a 100% sure but surly the difference is neglagible (close to zero) as to what floor finish it is? I have low flow temps and engineered wood floors. Perhaps makes more difference if insualtion is low below it.

Edit. It might also make it slower to heat, but no heat should actually be lost

Cyrus

https://www.boards.ie/discussion/comment/121660972#Comment_121660972

i wouldnt have thought so, we have tiles in a downstairs look and the floor is very warm, the wood floors get lukewarm, i believe wood is an insulator rather than a conductor, so you use more heat to get the room up to temp, we were told that at the time as well but we wanted hardwood floors (engineered is better but not as good as tiles or polished concrete apparently)

graememk

Wood is an insulator, it would slow the conduction of heat though the floor Vs tiles that are stuck to the screed floor.

MicktheMan

https://www.boards.ie/discussion/comment/121659145#Comment_121659145

The ventilation system will do very little to help balance the temperatures throughout the house because the volume of air moving is minuscule compared to what would be needed to have an appreciable effect (specific heat capacity of air is tiny compared to, say, water).

Eleusis

The research I did before renovations led me to realise that the floor finish made almost no difference to heat loss so I chose wooden floors. Yes wood is an insulator and tiles may feel warmer and react faster, but the U value of wood is so low, it would have little to no affect vs insulation below the slab. It will be slightly slower to react but it won't stop heat from getting through in any meaningful way. Where else will the heat go? Also heat rises naturally.

However a suppose if your not heating it 24/7 and instead heating when needed such as in the morning or when you get back from work then it would make a difference as it will heat slower, but for heat pumps it's not really the way they want run for efficiency.

Cyrus

https://www.boards.ie/discussion/comment/121661624#Comment_121661624

OK good to know I leave ours at a constant 21 degrees downstairs, we had a power cut with the storm and it took a good while to get back up to temp but I guess thats when you see the inefficiency, maybe keeping it at temp continuously then not so inefficient

newhouse87

For me running 24/7 is more costly. Setback overnight where house drops 1 deg is fine with me.

Eleusis

https://www.boards.ie/discussion/comment/121661949#Comment_121661949

I did this for a while too when running on room temp instead of WC. A little drop back overnight was better for me too

ColemanY2K

https://www.boards.ie/discussion/comment/121660173#Comment_121660173

I'm just about finished or as finished as a self build can be at time of moving in haha.

As for the air tightness test I did indeed get a fella in to do the blower test. It's a traditional block built house so i got him in just before second fix. Most of the leaks were where the wall was chased. Even though the chase was coated with air tight paint air was escaping out the top of the chase despite using expanding foam to "seal" it.

Photos below taken from attic looking down at the top of the internal walls between the joists.

mitresize5

Hi,

Had looked for recommendations to reduce usage a few day back (details below)

I have reduced the temperature on the stats by 1 degree upstairs and downstairs.

I have taken note of the the flow temp over the last few days and nights and it has ranged from 30 degrees to peaking at 54. More often than not in the 40's.

Is this my problem?

reminder of set up

Bill 860e - 2156 units used in billing period. Nothing to compare it to as we weren't in the house last year.

House is block built with 72.5mm internal insulation and pumped cavity, 600mm insulation in the attic, triple glazing new windows and doors

House size is 2350sq feet

Underfloor under polished concrete downstairs, radiators upstairs

Panasonic 9Kw heat pump

DHW set to 54 degrees - seems excessive

Stats set to 22 downstairs and 20 upstairs, have dropped them by 1 degree each

Eleusis

https://www.boards.ie/discussion/comment/121662064#Comment_121662064

You can get expanding foam specific to air tightness. More expensive though. Not sure if it makes much of a difference over the normal stuff but it certainly seemed better. This the stuff I used

https://www.dekah.ie/products/soudafoam-wundow-door-sws-gun-foam

newhouse87

https://www.boards.ie/discussion/comment/121662264#Comment_121662264

Flow temps def the issue. Should never be in 40s not to mind 50s. Your curve is too high. Few of us using g fixed low and happy with it.

NedNew2

https://www.boards.ie/discussion/comment/121662264#Comment_121662264

This calculator, while basic, gives a rough estimate of how many kWh a house of your size (220 sq. metres) would use annually.

https://ecoplus.ie/heat-pump-kwh-cost-calculator/

It comes in at around 6,600 when using the default values - of which maybe c75% is used in the winter months. If you've used 2156 in two winter months then it looks like you're usage might be slightly above average but not excessively so.

It's just a guide of course.

mitresize5

https://www.boards.ie/discussion/comment/121662294#Comment_121662294

thanks - can you elaborate 'using g fixed low' means

Also I understand that the flow temp is the temp of the water in the system. What does limiting that do, are there trade offs for that? Like why would it ask for temp in the 50's if it didnt need it

ColemanY2K

https://www.boards.ie/discussion/comment/121662286#Comment_121662286

I solved (or at least I hope I have) the issue by making a very strong mix of mortar and pouring it down the chase from above to form a plug.

I had asked the fella who was cutting the chases not to go above the final row of blocks but he looked at me like I had two heads.

Trying to get across to the trades small details in order to get a house to passive standard was an uphill battle, especially those who've been in the game 20 or more years and only know one way of doing things.

Anyway fingers crossed the airtightness score comes down as the lower it is the less the heat pump will be needed.

newhouse87

https://www.boards.ie/discussion/comment/121662341#Comment_121662341

Fixed flow is the temp of the water circulating in ufh pipes. Cost more to heat the water so .lower flow temp the more efficient and cheaper it will be. Fixed flow vs weather curve. Yours is on Weather curve as it varies with outside temperature, colder outside the higher your flow temperature goes. Fixed flow is running lowest flow temperature regardless of outside temperature. Goes into 50s as your installer was probably clueless and didn't want call back.

staples7

https://www.boards.ie/discussion/comment/121662264#Comment_121662264

€860 before government €150 credit?

mitresize5

https://www.boards.ie/discussion/comment/121662423#Comment_121662423

this is great info - thanks.

If I go with Fixed Flow does it affect being able to keep the temperature in the house at that on the stats. it seems counter intuitive, I can see why reducing the flow temp will save on usage but if its not as high will it struggle to heat the house?

Not second guessing you - just keen to get an under standing