Heat Pump for a Semi-Detached House
Estimate the Saving for a Semi-Detached House
Pre-set for a 3-bed semi-detached on gas with the standard SCOP 3.5. Older semis may need £1,000-£3,000 of insulation work first to keep flow temps down.
1. What heats your home today?
Pick whichever your main heating uses.
Add up last year's bills, or use the typical figure for your home below.
3. What size is your home?
We use this to estimate the size of heat pump you'd need.
4. Do you have solar panels?
Free electricity from your roof cuts what the heat pump costs to run.
5. Your options
Most homes qualify for both. Leave them on unless you know they don't apply.
Your estimated saving
£230a year
Over 15 years that's around £3,456 off your heating bills.
Now: Gas boiler
£1,300 / year
With heat pump
£1,070 / year
You save
£230 / year
What about the upfront cost?
- Heat pump install (typical)
- £11,000
- Less government grant
- -£7,500
- You pay
- £3,500
- A new gas boiler would cost
- ~£2,750
If your boiler needs replacing anyway, the heat pump costs about £750 more upfront - earned back in roughly 3.3 years from running cost savings.
Like the look of £230 a year?
These are estimates. The only way to know your real saving is a free quote from an MCS-certified installer. Takes 2 minutes, no obligation, no pushy sales calls.
How we worked this out
Energy prices: Ofgem price cap for April-June 2026 (Direct Debit, GB average): gas 5.74p/kWh, electricity 24.67p/kWh. Heat pump tariff blended at 20p/kWh (typical for E.ON Next Pumped, EDF Heat Pump Tracker, Cosy Octopus on a heat pump load profile). Heating oil 11.21p/kWh (116p/litre ÷ 10.35 kWh/litre, April 2026). LPG 11p/kWh midpoint of typical UK domestic range.
Heat pump efficiency:Seasonal performance factor (SCOP) of 3.5. The real-world average across 252 monitored UK heat pumps on heatpumpmonitor.org is 3.87 (January 2026), so we've picked a deliberately conservative figure.
Typical bill ranges: Gas 3-bed £1,000-£1,400, oil £1,500-£2,000, LPG £1,400-£2,200, electric storage heaters £1,500-£2,500 (Uswitch, retrofitplanner.co.uk, Checkatrade 2026). Oil and LPG homes pay roughly twice as much per unit of heat as gas, which is why the saving from switching to a heat pump is bigger.
Solar: A typical UK 4kW system generates around 3,800 kWh/yr. Without a battery the heat pump can self-consume around 1,000 kWh of that; with a battery shifting midday surplus into morning and evening, around 1,700 kWh.
Install costs: Energy Saving Trust 2026 typical range £10,000-£13,000 by home size. New gas boiler ~£2,750 (UK average, Checkatrade 2026). The £7,500 grant is the Boiler Upgrade Scheme (gov.uk) for England and Wales.
Estimates only. Your actual saving depends on the installer, flow temperatures, your home's heat loss and your electricity tariff. Always get a heat loss survey from an MCS installer for an accurate quote.
Heat Pumps in Semi-Detached Houses: A Solid Match
Semi-detached houses make up a huge chunk of UK housing stock, and they're well-suited to heat pumps. You've got one party wall (less heat loss than a detached house), usually decent outdoor space for the unit, and in many cases, the insulation work has already been done. Let's look at what you're actually dealing with.
Heat Loss: More Than a Terrace, Less Than Detached
A semi-detached sits in the middle of the heat loss spectrum. With one shared party wall, you lose less heat than a detached house, but more than a mid-terrace with two neighbours. A typical semi (depending on age, size, and insulation) loses somewhere between 10,000 and 16,000 kWh of heat per year.
That range drives the system size decision. Well-insulated: you're looking at a 7–8kW heat pump. Poorly insulated, larger property: you might need 9–10kW. Get a heat loss survey done before accepting a quote. It's not something you want guessed at.
Insulation: What Do You Actually Need?
The answer depends entirely on your home's current state. Here's how to think about it:
If cavity walls are already filled and loft is insulated
Good news: you may not need to do anything before installation beyond checking your radiator sizing. Many semis built post-1990 or updated in the last 20 years are already in reasonable shape. Ask your installer to confirm with a proper assessment rather than assuming.
If cavity walls are unfilled
Get them filled. It's quick, cheap, and makes a significant difference. Cost: £450–1,000. Do this before the heat pump goes in.
If your loft insulation is thin or missing
Top it up to 270mm. Cost: £400–800. Again, do this first. It's the easiest heat loss you'll ever fix.
If walls are solid (older semis, some 1900–1920s stock)
You're in Victorian territory. Internal or external wall insulation becomes necessary, which adds cost and complexity. See our Victorian house guide for the full picture.
The Outdoor Unit: Side of the House Is Usually Ideal
Most semis have side access: a gate and passage down the side of the house to the back garden. This is a great location for the outdoor unit. It's out of sight from the front, sheltered from the worst weather, accessible for maintenance, and close to the house for short pipe runs. If you don't have side access, a rear garden ground mount works just as well.
Planning permission isn't usually required. Heat pumps on the side or rear of a semi are typically permitted development, as long as noise limits are met and you're not in a conservation area.
Radiators: Do a Proper Check
Heat pumps run at lower flow temperatures than gas boilers. If your radiators were sized for 70–80°C flow (as most are in a gas system), some may be undersized for the 45–55°C flow that a heat pump delivers efficiently. Your installer should calculate this room by room.
In a typical semi with good insulation, you might need 3–5 radiator upgrades. Budget £800–2,000. If you're planning a kitchen or bathroom renovation anyway, underfloor heating in those rooms is a great complement to a heat pump.
Cost Breakdown by Insulation Status
| Insulation Status | Insulation Cost | Heat Pump Cost | Total Before Grant | After £7,500 Grant |
|---|---|---|---|---|
| Well insulated (no work needed) | £0 | £9,000–12,000 | £9,000–12,000 | £1,500–4,500 |
| Cavity walls + loft needed | £850–1,800 | £9,000–12,000 | £9,850–13,800 | £2,350–6,300 |
| Plus partial radiator upgrades | £850–1,800 | £9,000–12,000 + £800–2,000 | £10,650–15,800 | £3,150–8,300 |
Running Costs
A well-insulated semi with a correctly sized heat pump typically runs at £800–1,100 per year for heating and hot water. On a standard electricity tariff, that's broadly comparable to gas for many people, but on a time-of-use tariff (Octopus Agile, Cosy, or similar), you can push heating costs significantly lower by running the system during cheaper overnight slots.
Most people switching from an older gas boiler in a semi see bill savings of £300–700 per year. The payback period depends on your current setup, but for a semi with decent insulation and a fairly aged boiler, the numbers typically work out well.
Is Your Semi a Good Candidate?
Ask yourself:
- Do you have cavity walls that are already filled? (Check with your insurer or council, as many areas had mass cavity fill programmes in the 2000s)
- Is your loft insulation at 270mm or more?
- Do you have side or rear garden space for the outdoor unit?
- Is your boiler more than 10 years old?
If you answered yes to most of those, you're in good shape. The net cost after the Boiler Upgrade Scheme grant can be surprisingly affordable, and the long-term running cost savings are real.
Ready to fit one in your semi?
Get free quotes from MCS-certified heat pump installers near you.
More: How the £7,500 heat pump grant works | Heat pump running costs | Do you need new radiators for a heat pump?