I’m spending a fortune running a heat pump in my build! Please HELP 😫

[damspt]

On 21/11/2025 at 09:08, MikeGrahamT21 said:

What size, type is your property and how well insulated is it?

@MikeGrahamT21 It's a 3 bedroom semi detached house and I think it's well insulated by what the professional snagger has told us

[damspt]

On 21/11/2025 at 09:11, JamesPa said:

Its very cold at present, this is the time it will be at its most expensive (roughly double what you might normally see most of the season), Dont forget to factor that in!  With a cost of £6 presumably about 24kWh? - difficult to tell as you are apparently on agile (do you have a battery?  If not agile might not be the best tarrif)

 

For comparison Im currently consuming about 28kWh/day in a house with a loss of 7kW @ -2 and on the few days when its consistently sub zero I can consume as much as 50kW.  The heating is still cheaper and more comfortable than the gas boiler it replaced was, so Im not complaining!

 

You seem to have your WC set to 49@-2 and 39@20.  Does it need to be that high (answer no, certainly at the high OAT end)?  Are you operating 24x7 with WC adjusted and zones balanced, thermostats/trvs set to max so they have no effect or alternatively 2C above desired so they act as limiters?

 

Tell us a bit more and someone may be able to give some specific suggestions.

@JamesPa Hi, it's my first winter with a heat pump in my new build so all a bit new for me. I don't have a battery, not even sure how they work and if it's worth it for me. I actually want to know a bit more about it, are batteries worth it and expensive?

What does OAT mean? I'm not sure if it needs to be that high, it was set by a heat pump professional. Yes, I think it's 24x7 with WC. Trvs are all set to max all over the house.

[Oz07]

This thread could not be a more perfect example of the level of understanding the average person has of their heating system.

[damspt]

On 21/11/2025 at 09:24, ProDave said:

As above questions a LOT more information needed.

 

How old is the property? How big etc.  And your approximate location,

Is the Heat pump new?  Does it replace a previous heat source, e.g. a boiler, if so how much did that cost?

 

It is not easy to apportion heat pump consumption from a total electricity bill, I know exactly how much mine uses only because I chose to fit my own electricity meter to record just what the heat pump uses.  The best you can do is compare the daily usage now, with daily usage in the summer, if you do that you get an idea how much additional electricity is being used by the heat pump.

 

 

@ProDave Hi! It was build last year and we moved this year in February. 3 Bedroom semi detached house. East midlands. Heat pump I'm guessing it's new since it's a new built. 

 

I had a look at my daily usage in the summer and it was around 347.40 kWh for the all month of August, Lowest was around 6kWh and high was about 17kWh

[damspt]

20 hours ago, canalsiderenovation said:

 

Is this all electric house, cooking etc all electric? We are using pretty much the same during this cold snap too but that's everything. We had temps down to -6 for 2 nights on the run though so very, very cold.

@canalsiderenovation Hi, yes it's all electric! -6 is damn colddd

[SteamyTea]

@damspt

 

UFH = under floor heating

OAT = outside air temperature

IAT = inside air temperature

DHW = domestic hot water

WC = weather compensation

kWh = energy

kW = power

 

[JohnMo]

18 minutes ago, damspt said:

@JohnMo Yes, Agile tariff which seems to be the best by comparing with others. Please let me know what are the terms for DHW and CH as I'm new to this and have no idea what those initials are for. 

DHW is domestic hot water, so your hot water cylinder used for water that comes out of the hot tap.

 

CH is central heating so radiators and/or UFH (under floor heating - heating with pipes buried in your floor).

 

Hope this helps.

 

So a couple of things for you to do

 

Check your actual heat pump consumption and then you have the house consumption (octopus) and you heat pump consumption (Panasonic controller) and you can really see what your heat pump is doing.

A video here to show you how to get the figures for the heat pump 

 

 

Next do you have a buffer, this is likely to be a smaller cylinder about a quarter to half the size of the main hot water cylinder.

 

Next take some photos of your install both outside and inside, showing pipes and all the main items if the install.

Edited 13 hours ago by JohnMo

[JohnMo]

12 minutes ago, damspt said:

batteries worth it and expensive

That's another thread don't let this go off on a tangent you will never see an answer

[JohnMo]

13 minutes ago, Oz07 said:

This thread could not be a more perfect example of the level of understanding the average person has of their heating system.

Yep been there, but everyone learn - every day's a school day 

[marshian]

20 minutes ago, Oz07 said:

This thread could not be a more perfect example of the level of understanding the average person has of their heating system.

 

WHS ^

 

After Council Tax the Central Heating "CH" and Domestic Hot Water "DHW" costs are the biggest expenditures in running a home (excluding food because it's based on household size)

 

Minimising those costs can result in a decent annual saving.

 

@damspt what room temps are you targeting - one of the benefits of a low temp heating regime (be that ASHP, GSHP or low temp gas boiler) is you can reduce room temps compared to traditional UK scheduled heating regime where you blast the house with heat during times of occupancy and then allow it to cool down outside those periods. 

 

I'm running Bathrooms at 20, Living spaces at 19 to 20, Bedrooms at 18 to 19.5 and all other areas 17 to 18.

 

Moving from room to room you don't notice the small temp differences and the whole house feels "comfortable"

[damspt]

21 hours ago, Nickfromwales said:

Are you using the heat pump to do hot water in this bitter cold snap? 
 

If so, your unit will hate you for it as it’ll be frosting and defrosting a bunch on low grade heat but will be much more of an efficiency killer when heating hot water. 
 

Try 48 hrs topping up with the immersion ( in off peak windows ) and see if that improves things. 
 

Also how long is the heat pump taking to recharge hot water? If it’s a long period then the house will start to cool down making the job of maintaining comfort temps even harder.

@Nickfromwales Hi, how else would I use hot water? I only have heat pump. 
How would that work topping up with immersion? I don't even know how to work with that haha. 
I don't know how long is taking to recharge the hot water, I only have a thermostat in the lounge and the octopus app. Some of you have greater detailed apps somehow which I wish.

[damspt]

20 hours ago, Beelbeebub said:

Could the Op post the kwh usage graph from. Octopus. 

 

Thry say they are on agile which has a massive spike between 4-7pm (eg today 21st Nov it's neatly 50p/kwh)

 

Agile is for people with a battery (mostly) 

 

For a HP you need a Cosy tariff. 

@Beelbeebub Hi, unfortunately between 4-7pm is the only times we have time to cook and have a shower! I compared my costs with cosy tariff with the "octopus compare" app and Agile it's still better than Cosy

[damspt]

18 hours ago, canalsiderenovation said:

It works for us, three periods of cheap electric, 4am til 7am, 1pm to 3pm and 10pm til noon. We work from home and only heat the house those times although the stat is set at 18 degrees as a set temp we have it heated up more during Cosy so manages to retain the temps. Works for us...

@canalsiderenovation can you show me your weekly timer and weather curve please? 

[damspt]

17 hours ago, Nestor said:

To reply to others type the @ symbol then a letter, names will pop up, scroll down to find the poster you wish to reply to.

Give it a try.

@damspt

@Nestor thank you so much man!

[ProDave]

26 minutes ago, marshian said:

After Council Tax the Central Heating "CH" and Domestic Hot Water "DHW" costs are the biggest expenditures in running a home (excluding food because it's based on household size)

Not in my house.  Council tax is more than twice my total energy costs.  But unlike energy costs I can't do anything to reduce it or swap suppliers for a better deal.

[damspt]

16 hours ago, Beelbeebub said:

If you used 31kwh yesterday (20th) that's pretty good. 

 

The 20th was pretty cold (dunno where you are but it was sub zero across the Midlands). 

 

If we assume your house uses something like 6kwh a day for non heating stuff like fridges and lights, then you used 24kwh in a day, basically 1kw continuous heating load. 

 

If we assume a cop of about 2.5, that's a heat demand of around 2.5kwh. Not unreasonable for a house kept at 22-24C during a subs zero cold snap. 

 

If I read your graphs correctly on the 20th you used 31kwh and paid £6.52. That's 21p per kwh.

 

Coukd you post some pairs of graphs for the kwh in a given day, then the £for the same day.  I suspect you are losing out by using some energy during the agile peak period.  You could save a fair bit by making sure your hot water heating doesn't occur then and also maybe turning your heating off for those hours. 

 

Agile is best used with some sort of automatic system that adapts your use to the variable daily price curves. 

 

You migbt get a better price using Cosy. 

@Beelbeebub Hi, some graphs for the 17th. I guess i'm worrying too much? as some of you are spending more than me but it's very scary what we will end up paying. I have compared cosy tariff using the octopus compare app and agile it's still better than cosy tariff. 

yes we do use a fair bit at peak hours because that's when me & partner come from work and cook and shower the baby. It's annoying how they make sure we use the peak times because there is no other option

 

do you use agile? would like to see a weekly timer setup from you

[damspt]

16 hours ago, JohnMo said:

Not sure why you think the electric consumption is high. Assume you are all electric etc.

 

Our house seems to use about 20kWh without the heat pump.

 

 

@JohnMo I guess some people are spending more than me but still scary how we will end up paying during winter times unfortunately

[ProDave]

10 minutes ago, damspt said:

unfortunately between 4-7pm is the only times we have time to cook and have a shower! I compared my costs with cosy tariff with the "octopus compare" app and Agile it's still better than Cosy

With such a peak usage at the most expensive time, 4-7PM I suspect you might be better not on any form of Time Of Use tariff and just be on the standard fixed rate all day tariff.

 

Time Of Use tariffs only make sense if you can use most of your energy in the cheap times and as little as possible in the expensive times.  For most people with an all electric house it is impossible to avoid usage in that 4-7PM slot.

 

P.S just "having a shower" in that peak time need not use any energy.  The hot water comes from your hot water tank.  Just adjust the timer for the water heating so the ASHP does not immediately start re heating the water until after the 7PM expensive period finishes.

[marshian]

6 minutes ago, damspt said:

@Nickfromwales Hi, how else would I use hot water? I only have heat pump. 
How would that work topping up with immersion? I don't even know how to work with that haha. 
I don't know how long is taking to recharge the hot water, I only have a thermostat in the lounge and the octopus app. Some of you have greater detailed apps somehow which I wish.

 

You don't need detailed apps - you just need to understand the process that is going on regarding your DHW and CH 

 

Example if it helps (Gas boiler)

 

I heat my water every day at 6.00 am to 6.30 am - as a result of this I can download the half hourly energy data from Octopus and I know that the duration and energy cost of providing the house with DHW 

 

I'm running CH 23.5/7 (with DHWP "Domestic Hot Water Priority so for 30 mins my house doesn't get CH) with WC 

 

We still cook with gas but that's pretty much a constant and only amounts to 1% of our annual energy usage

[damspt]

16 hours ago, SteamyTea said:

@damspt

 

Does that price on your charts include the daily charge and VAT?

 

4 quid a day seems quite low to me, mind you, yesterday I used 6 kWh, and I had a light frost on the car this morning (only one at work that did, but then I start earlier than the idle buggers).

Your chart shows a higher usage during the evening, are you doing a lot of cooking and clothes washing/drying.

A faulty fridge can burn though quite a bit of juice, check it to see if it constantly running (touch it and feel the vibes).

 

Much warmer when I left work half an hour ago. South West wind now. So cold snap is over.

 

This is what it was like earlier.

Not much difference in temperature, but windier, and from the North, which is rare down here (we had snow in Bodmin).

 

 

 

 

@SteamyTea this is now with the daily charge! yes unfortunately most peak times we end up cooking and using the shower as that's when we come back from work and get son from nursery

[marshian]

3 minutes ago, ProDave said:

Not in my house.  Council tax is more than twice my total energy costs.  But unlike energy costs I can't do anything to reduce it or swap suppliers for a better deal.

 

Isn't that what I said??

[damspt]

1 hour ago, Marvin said:

Hi @damspt

 

There are so many considerations when discussing ASHPs.

Although I am not a fan of EPC's I would be interested to know what rating your house is.

If you look up your home on the EPC register it will tell you lots of things which are questions you would be asked here. For example:

Is your home rated A B or C.  The Floor area and the calculated kWh use per year for heating: If you divide the kWh by the floor area this will give you the amount of heating in kWhs per square metre floor area per year. 

 

From my own experience with our ASHP over the last few years we are satisfied with the results.

Our ASHP uses masses during cold weather but almost nothing during the rest of the time. 

We run at about 22 - 23 degrees C during the winter.

We also have a MVHR system and PV.

 

So when you compare our little bungalow to @Nickfromwales's home we would use kWh per year per square metre of floor. (don't do it Nick you would only be depressed😆).

 

Good luck

 

M

 

 

 

@Marvin energy rating is B. Total floor area is 84 square meters.

[damspt]

8 minutes ago, ProDave said:

P.S just "having a shower" in that peak time need not use any energy.  The hot water comes from your hot water tank.  Just adjust the timer for the water heating so the ASHP does not immediately start re heating the water until after the 7PM expensive period finishes.

@ProDave yes! that's actually something i don't really understand why we spending so much when having showers if the water is already hot. 

how do i adjust the timer for the water heating? i think from what i remember, they set it up for 2am tho, so not sure how it's still working during shower times

[damspt]

40 minutes ago, marshian said:

 

@damspt what room temps are you targeting - one of the benefits of a low temp heating regime (be that ASHP, GSHP or low temp gas boiler) is you can reduce room temps compared to traditional UK scheduled heating regime where you blast the house with heat during times of occupancy and then allow it to cool down outside those periods. 

 

I'm running Bathrooms at 20, Living spaces at 19 to 20, Bedrooms at 18 to 19.5 and all other areas 17 to 18.

 

Moving from room to room you don't notice the small temp differences and the whole house feels "comfortable"

@marshian i have no idea the temps of each single room, only have 1 thermostat in the lounge. It feels colder in our main room, baby bedroom ( which both are upstairs ) and i guess the lounge which has french doors and a view to a field

[Marvin]

6 minutes ago, damspt said:

@Marvin energy rating is B. Total floor area is 84 square meters.

Hi @damspt

 

What was the expected kWh year requirement?