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Heat Pump Sizing & Installation Costs

 
Air Source Heat Pumps (ASHPs)
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4369
Topic starter 10/03/2025 9:09 am  

I’m doing some research for an upcoming article and podcast, and I’d love to gather some data from our homeowners on the forums that have installed heat pumps. If you’re willing to share, it would be massively helpful!

What I’m looking for:

• Property size (in square metres)

• Heat pump size (in kW – e.g. 5, 6, 12kW, etc.)

• Approximate installation cost (heat pump, labour, etc.) 

If you’re happy to share your figures publicly, please post them in this thread. If you’d rather keep the cost private, feel free to DM me or email me at @renewableheatinghub.co.uk" target="_blank" rel="noopener">editor@renewableheatinghub.co.uk

Info sent to me in private will be kept confidential and will only be used for statistical purposes.

Thanks in advance to anyone who contributes.


This topic was modified 1 year ago by Mars

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 Tim441
(@tim441)
Honorable Member Contributor
Joined: 3 years ago
Posts: 398
10/03/2025 11:29 am  

Perhaps useful to have installed date too? To get context...my example:

LG Therma V 16kw monobloc

Installed Aug 2020 replacing oil

Approx £12k. Included replacement hot water tank and one radiator. RHI grant 

200 sq m (100 sq m listed building, poor insulation. + 100 sq m modern extension with excellent insulation). Underfloor heating downstairs throughout.

 


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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 Adrian
(@adrian)
Trusted Member Member
Joined: 1 year ago
Posts: 38
14/03/2025 5:59 pm  

100m2

5kw 

£11000-£7500=£3500 pick 3 radiators 



   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 4476
15/03/2025 8:25 am  

2024

200sqm

7kW

200l UVC

2 new rads, one new fancoil, one existing rad relocated (total 4 rads changed)

16A feed for heat pump already in place so not included

£12,450 less grant = £4,950 net  

Work duration - 6 man days of approx 9 hours each


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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Abernyte
 Abernyte
(@abernyte)
Reputable Member Member
Joined: 3 years ago
Posts: 258
15/03/2025 8:52 am  

2019

180sqm timber frame

14kW

300l DHW

16 new rads K2 and K3, new delivery pipework, new electrical consumer unit

£12,200 less RHI (Scot) £13,200 over 7 years

6/7 days for 2 heating engineers and 1 sparky

 



   
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 JohnR
(@johnr)
Estimable Member Member
Joined: 1 year ago
Posts: 106
16/03/2025 1:06 pm  

1970s 4-bed detached house approx 168 sq.m internal area in central southern England. Approx 200mm of roof insulation, insulated cavity walls, fairly recent double glazing including a 3m wide two storey north facing widow which is triple glazed but a heat loss due to its size (big curtain closed in autumn and opened in spring).

£16,600 for 7kW Vaillant Arotherm+ heat pump including SENSOcomfort controls, SENSOnet gateway, Telford Tempest 250 litre combined DHW cylinder / buffer tank and 11 new radiators.

Installation took about 20 person-days of work. There was significant pipework modification to accommodate larger radiators and one new radiator and probably above average work to connect the heat pump as it was two rooms away from the cylinder (placed in what I considered to be the most convenient location).

I suspect I paid a generous price but it was the only convenient quote from an installer who appeared to understand the technology and I wanted the work done during the summer (Octopus offered a lower price but with a likely installation well into the autumn and would only change such radiators as they deemed necessary). Radiator replacement was steered by both the heat loss calculation which I compared with my own estimate, my knowledge of where more heating was needed and my desire to replace all radiators which weren't 21st century. The work was done competently and fitted in with my own needs such as radiators were removed and I was given a few days to do decorating before new ones were fitted.

The 7kW sizing seems to be correct. The maximum hourly output so far according to the Vaillant app was 7.6kW for 7 to 8am on 11th January when the outside temperature was -7C and the heating had been turned up after a modest overnight setback. However, I suspect that Vaillant are over-estimating the output as a daily COP of 3.9 for that day (mean temp of -3.7C) is almost implausible. Nonetheless, generous radiator capacity keeps the flow temperature below 40C under the worst conditions.

More details of the work are attached.

JohnR ASHP work schedule.pdf


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1693
18/03/2025 2:31 pm  

Ours is a 1930s bungalow with extension and loft conversion and is now about 105 sq m. Generally well insulated but we did replace french doors, front door and two small kitchen windows that were all found to be losing more heat than they ought.

We replaced our oil boiler with an 8.5kWh Mitsubishi Ecodan in December 2021. No radiator changes were needed but there was a reasonable amount of pipework needed replacing with wide bore pipework and a new hot water tank was installed as well. They also had to install a separate sub board specifically for the heat pump to avoid tripping the switch on startup (which it initially did intermittently). In total it cost £15k inclusive of the vodka and tonic, but given the RHI it came to a net cost to us of about £4k. The guys spent about 5 days on site including the troubleshooting that eventually led to the installation of the sub board.

The subsequent three years or so have shown a number of areas which are frequent forum bugbears that our guys did right unbeknownst to us (newbies that we were back then). No red flags were raised then nor any since and our bills have dropped markedly as a result.

I should also say we then opted for their 5 year maintenance plan for another £950 hence a squidge under £200 per year which has subsequently been shown to be reasonably good value, particularly since each time they've turned up to do the servicing I've seen them actually working for their money rather than just tinkering. Is it money for old rope? Probably. Is it a rip-off? At that price and given the attention they show, no. Are we satisfied? Absolutely.


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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