In the UK, the prices are high because the marginal cost is a government run scheme (MCS) and only the very keenest of people install these systems today. That scheme is about training installers. Heat pump installations are unecessarily complex and costly at the moment (oversized, over specified and demand outstrips supply).
I note that the cost of heat pumps has doubled over the last few years. This reflects the fact that heat pumps are a niche product.
Great insights @jchidley and congrats the high performing self-install!
The high level of the current BUS grant does concern me, together with the impression I get from installer conversations elsewhere on the paper work overhead of MCS. There must be a more cost effective way of supporting the industry!? I do worry that the industry is just headed for another boom bust cycle. That my feeling about it but my area of expertise is definitely not policyā¦ I donāt want to go on a big tangent here on that side of things but it would be interesting to think about what the future of heat pump installations could look like under a much lighter subsidy e.g Ā£2-3k per heat pump or even un-subsidized.
It would help if the government/Ofgen unlinked gas and electricity prices. Then they could just increase the gas price (to discourage its use and help reduce CO2 emissions) and that would automatically increase the DCF of new heat pump projects, even with little or no subsidy.
Doesnāt help us existing owners thoughā¦
Anyone that currently has a well performing heat-pump system has done all of the hard work. Itāll be cheap for someone else to replace the current heat pump for a better one.
Also, would anyone go back to a gas boiler? I love my house being warm and also those gas boilers are noisy.
Maybe they can be thought also as an investment into the property.
You can change a old kitchen for a newer one and that makes your property more attractive when being sold making it worth more. And in the meantime you enjoy a nicer kitchen.
I would think the same way about viewing a property that has a heat pump, so all the work of adding a cylinder and upgrading radiators and reconfiguring pipework has already been done and paid for. Therefore I donāt have to factor that in as a future cost making the property more attractive to buy.
I know we arenāt in that place yet but as boilers start to be phased out Mr and Mrs Jones might start looking for that as well. Just imagine on āhomes under the hammerā if they comment on that sort of thing rather than pointing out the property has a āmodernā combi-boiler.
So what Iām trying to say is Iāve spend all this money now but it should either save me money in the future that I would have to pay anyway when boilers have been phased out and my current one dies or it adds value to my house for the future.
Then the reduced running costs, reduced CO2 emissions and improved comfort are all bonuses and reasons for doing it now rather than waiting.
So for all of this I would ignore the cost of the actual heatpump as this is a replacement cost against a gas boiler whereas all the other bits is where the value lies.
/end ramble
Hi @Alan_Bennett, welcome to the forums 
I just saw your comment here and the numbers jumped out at me as feeling a little offā¦ a good rule of thumb for the peak heat demand / heat loss is to take the annual gas consumption and divide by 2900 - there is a good article/video on that here: What Size Heat Pump Do I Need? A Rule of Thumb | Protons for Breakfast
You mentioned that the heat loss is a guess at 20kW, but on this rule of thumb it might actually be nearer 11kW [assuming that the annual gas usage figure is about right, of course] - and if youāre in the process of adding more insulation and reducing the heat loss further then it could even be less than this.
If youāre in no rush to get a heat pump, itāll be worth taking readings on the coldest days over the coming winter to see what the highest gas usage is.
Just thought it was worth a mention, since it seems possible that youād be fine with a single heat pump rather than 2 which would be a fairly substantial saving in upfront costs.
Hi. Thanks for the info.
I had a smart meter fitting in 2016.
Only 30 minutes meter readings from March this year.
Iāve looked back at gas usage Jan, feb
This Jan Feb is 31398 kwh of gas.
32342 kwh for last year.
In 2022 34559 kwh. Two bathrooms being fitted in Jan that year and working on the hallway.
The two covid years where high gas as everyone was at home.
Looking back I can see what I was doing to the house and how it affected the gas usage.
Last two years Iāve done very little to the house indoors so Iām going off those readings for gas usage.
I forgot to mention that I have a wood burning stove. A 8kw. On the colder days itās on ticking away. The lounge is a big room. 9m x 5.5m.
Room has two rads. Type 22.
2000x500 and 1400x600. If the heating is on the room is comfortable but if the central heating is ticking away you can feel a little drop in the lounge. Thereās 3 outside walls in the lounge. Hopefully insulating the crawl space will have a impact in this room.
A snap shot of house heating
Time. 20:57.
Outside temp 6c
Rads warm to the touch.
Flow temp on the boiler is say 44c. Boiler is a Worcester 40cdi. 16 years old.
Stove on but low.
House is at the temp of the thermostat, 19.5c
18 radiators
4 bathroom towel rads.
1 rad old type.
2 type 21
11 type 22
All internal doors open as we have kids and two cats!
For a 100 year old house thatās 306mĀ² 9" solid brick walls. Not too bad.
Iāll probably get a ASHP installed next year as the boiler has something wrong every year.
The boiler has got to the point that know one will work on it anymore because of its age.
The main reason to crawl around under the floor is to be able to have one heat pump setup.
Next year Iāll get a local heat geek elite to do a heat loss. Ā£500 though! Ouch.
If I say the boiler is running at 85% efficiency gas to heat the house is 28000kwh.
Letās see what the heat loss says.
Thanks.
My annual gas consumption was 21,000 kWh (or 21 MWh or the scientifically literate 78 GJ - gigajoule), That gave me a divide-by-2900 of 7 kW for the heat pump. My own detailed calculations, based on degree days and factoring in the boiler efficiency of 89% (the highest in the manufacturerās data) suggested 5kW.
The official calculators, online calculators, MCS, various accredited installers, firmly declared that 9kW to 14kW was ārightā.
I decided that 5kW was probably right and upgraded all of my radiators by a factor of at least 2. Iād say that the radiator and pipe upgrades is where you should spend your money (or underfloor heating).
If you go the MCS route then volumizers/buffer tanks and all sorts of other āstuffā will be forced on you which amounts to hundreds, if not thousands, of pounds of extra costs. I couldnāt get anyone to install the 5kW system that I wanted for a reasonable cost so I arranged it myself.
Upshot? It works perfectly and 5kW is big enough.
If I did it again, I would still upgrade the pipework and radiators, and stick with the 5kW Vaillant Arotherm. The only place that I nearly came unstuck was the water heating. My family got used to the higher flow and really hot temperatures of the temporary, immersion based, system. It took a while to dial back the flow rate.
Jack
Hi Jack.
The primary plumbing is 28mm. Rads are tead off to 22mm. Replacing the pipe work isnāt viable. All the radiators are around 9 years old. Thereās only one that we havenāt changed.
Iād understand I might need to change some rads to type 33, especially in the lounge.
Installing ufh again not viable.
Looking at the excellent formula posted by Steve. Using 80% boiler (16 years old) efficiency and 40000kwh of gas (worst case)
I come to a figure of 11.16 kw heat pump.
Using 32000 kWh of gas I get to a 8.9 kw HP. Crazy!
House is heated 2 hours in the morning and 7 hours in the evening.
Max temp 19.5c. Lowest is set to 18c.
Thanks all for your comments.
Alan.
Ps I finished insulating 14mĀ² of crawl space. Took 8 hours on my own. Only 100mĀ² to go!
We had
Weāve just moved to Octopus Cosy for this winter as Flux meant we were always charging the battery at the day rate just before 1600 so hopefully this winter will be cheaper than last. Someone is home all day so we keep a constant temperature between 0400 and 2000.
Before 2022 we used about 2500kWh of electric and 9500kWh of gas, we now use about 5000kWh and import about 2700kWh of that, we also export about 2400kWh.
We seem to be getting an SCOP of about 3.5 over the whole time itās been monitored, whilst running.
Weāre renovating the kitchen next year, and with the projected floor level rise of UFH if we donāt do it at the same time it wonāt get done. So hopefully weāll get a better COP next winter.
Thanks @irMonitoring! Interesting example. Great to see the solar figures so about 46% of demand supplied with the solar and battery. I was playing about with a simulation yesterday and worked out that I should get to ~48% with 4.8 kW solar and a 10 kWh battery so thatās a good confirmation that Im in the right range. Does that include an EV or just household loads and the heat pump?
@TrystanLea No EV, just normal loads and heat pump.
I think the SolarEdge designer predicted around what weāre getting, although when I did the calculations I hadnāt considered a HP.
Hi, Belgian experience here,
5 years ago we bought a 10-year-old 270 sqm house with a vaillant propane boiler with underground tank, underfloor heating and radiators upstairs. I didnāt know anything about underfloor heating or gas boilers, so I looked into how they worked, first by changing the thermostat so that it would finally modulate with an outdoor sensor, then by trying to balance the radiator circuit and the underfloor circulator ā¦ mission impossible, the boiler was too powerful, 8 > 25 kW, starts and stops constantly, causing thermal discomfort, from there start the idea of a heat pumpā¦
we consume about 1200L of propane, i.e. 14.000 kWh, about 1000ā¬/year we also make a small fire in the evening, 5 steres of wood per year.
We also have 12.7 kWp of photovoltaic panels on the roof ( 10 K Solaredge full South and 38 LG panels) , which have now paid for themselves, producing between 14 & 16,000 kWh on average. And 2 Tesla cars covering 70,000 km/year. DHW is done by a 300 L Thermodynamic boiler at 50Ā°C.
I thought Iād need a 12 kW heat pump, then last year I came across the heatgeek channel, then Urban Plumbersā, and after calculations I came up with the need for an Arotherm+ 7kW. On a sales site, I found an unpacked, never-installed 5 kW for 2,700ā¬, so I decided to try it out, keeping the gas boiler as a parallel hybrid installation if Iāve made a mistake in my calculations or the 55 isnāt powerful enough. It would kick in when COP is lower than 2.25, I hope never.
I redid all the primary circuit hydraulics in 28mm and replaced the floor distributor to balance everything properly.
The total cost was 4,500ā¬.
. 2700ā¬ for the Arotherm+ 55 heat pump
. 400ā¬ for the Vaillant electronic control module
. 1400ā¬ for the pipework and valves, etcā¦
Untill 2030, luckily in our region, I can count on my electricity meter ārunning backwardsā, which means that the grid acts as a battery, for around 850ā¬ of ātaxā per year. I now have untill 2030 to think about a huge battery setup. The annual solar production, which doesnāt cover our total consumption, will make the kWh cost me between 0.10 and 0.15ā¬/kWh.
Iām thinking of achieving a SCOP of 4 ( Iām over 5 for now on this November ) , i.e. a requirement of 3,500 kWh = ā¬450/year, so weād need about 8 years to pay off this installation. itās not a bad price to pay to free ourselves from fossil resources. not to mention that since itās been running, weāve finally got comfort, which we didnāt have with the gas boiler.
We are only at the beginning of our first winter with this installation, so to be continuedā¦
Thatās so good @Ulric congrats!
Thought I would try and summarize the examples given so far, thanks everyone! The TCO heat p/kWh is an interesting one, itās the 20 year electric cost + install cost before the grant divided by the 20 year heat output. Itās interesting that Damoās does so well due to itās high annual heat requirement. Itās probably not the best way to look at this, but certainly install cost per m2 of floor area or per kWh heat demand is a factor in the range of costs.
Very nice Trystan. Makes it really easy to appreciate the overall cost.
Itās interesting to add the comparative gas cost too; Iāve added 3 scenarios:
keep existing gas boiler, 6.24p @ 85% efficiency
=6.24/0.85
replace gas boiler with equivalent, Ā£2,500 + 6.24p @ 90% efficiency
=(100*2500/(20*J2))+6.24/0.9
upgrade gas boiler and some rads, Ā£5,000 + 6.24p @ 95% efficiency
=(100*5000/(20*J2))+6.24/0.95
Would it not be better to use the Net cost after the grant? It changes the TCO p/kWh quite a bit:
Edit:
average gross TCO (excluding self-installs) = 10.69 p/kWh
average net TCO (after grant) = 7.72 p/kWh
average TCO for replacement gas system = 8.16 p/kWh
Nice, great comparisons and actually interesting to see the effect before and after the grant. I was just interested to see what the unsubsidised TCO came out to but including the grant is more realistic for actual experienced economics in these examples.
Really interesting thread and different contributions.
I think it would also be interesting to contrast scenarios such as with/without an EV tariff, solar or batteries as the combination makes for an improved payback.
My situation:
EV received February 22, Ā£32,131 gross (-Ā£2,500 EV grant, -Ā£1,750 deposit contribution)
EV charger installed October 21, Ā£1,220 gross (-Ā£350 OZEV grant)
5.8kw solar & 9.5kwh battery installed May 2023, Ā£12,804.59 (zero VAT) 13 year payback estimated by solar installer
9kw Daikin heat pump, 180L cylinder, volumiser, 11x new radiators and sundries installed June 24, Ā£11,120 (-Ā£7,500 BUS, interest free trial by Octopus for 1 year)
Octopus service plan, Ā£9 per month for 5 years
Some points on the above:
Very happy with the synergistic benefits of multiple renewable technologies and whilst itās a high cost, Iām much happier paying for improvements which add to the value of the house and reduce my carbon footprint vs lining the pockets of oil and gas majors. Itās also been great learning about the technology especially the heat pump and setting up ESPAltherma and monitoring how itās working. Also the sense of community and hearing that others are passionate about this and optimising efficiency is amazing especially at a time when Trump is serving another term. Itās reassuring that people are empowered to make responsible choices and adopt heat pumps despite a lot of unfounded guff online about them. Iāll also show anyone who will listen my EmonCMS performance data to prove heat pumps work, and work incredibly well. Social proof is another benefit which is difficult to quantify and people I know have made positive choices as a result of data Iāve shared and hearing that itās a good experience owning an EV / heat pump etc.
Apologies itās a bit broader than the original request but thought it was useful context looking at cost of ownership. Would also be interesting to see whole life carbon emissions avoided by switching to a heat pump vs gas boiler and depending on tariff etc.
Hi Tim, does your scenario 3 assume installation of a weather compensation module on the gas boiler if itās hitting 95% efficiency? It astonishes me how many people have a new combi boiler fitted without one so the efficiency is constrained by fixed flow rate. Might increase cost marginally but would be more like for like with a heat pump system which more often includes weather compensation.
Yes, I had assumed some kind of efficient heating design that allowed the boiler to run at proper condensing temperatures, so some combination of bigger rads, weather compensation, sophisticated pump control or whatever. My cost estimate is very much a wet-finger-in-the-air kind, so apply salt liberally.
