Heat pump calculator the UK 2026
Enter your floor area, the condition of the property and what you heat with now. The calculator derives the heat loss, sizes the heat pump, compares annual running costs for every common heat source in the UK and tells you whether the investment pays back.
Required output
7 kW
Recommended heat pump output
Property heat loss
7.4 kW
Heat loss per square metre
62 W/m²
Equivalent full load hours
2,040 h
Real seasonal efficiency (SCOP)
3
Days a year using the immersion heater
0 days
Heat pump electricity use
6,290 kWh
Buffer tank / Hot water cylinder
140 / 240 l
Is a heat pump worth it for you?
No, a heat pump does not pay off with these parameters
- Running a heat pump would cost more than your current heating.
- Moving to a heat pump electricity tariff cuts running costs noticeably. Switch it on in advanced settings.
- A system running at 55 °C or above cuts efficiency. Larger radiators or underfloor heating improve the result considerably.
Payback and running costs
Never pays back
Payback period
Annual saving
-£206
Cost now → Cost with a heat pump
£1,580 → £1,786
Cost per kWh of heat
£0.084 → £0.095
per kWh of heat
Net investment after the grant
£12,600
CO₂ saved: 2.7 t/year
What this means: Compared with your current heating (mains gas) you would save nothing — running a heat pump would cost more.
What it hinges on
- A heat pump starts to pay off once the fuel price (mains gas) rises above £0.075/kWh.
- It starts paying off once electricity falls below £0.227/kWh.
Thresholds are indicative and calculated without price growth.
Annual cost by heat source
- Wood pellets£1,578
- Mains gas£1,580
- Logs£1,647
- Heating oil£1,658
- Heat pump£1,786
- Direct electric heating£4,873
Monthly heating cost
Cumulative cash flow
Every heating source compared
| Heat source | Annual cost | Cost per kWh of heat | CO₂ per year |
|---|---|---|---|
| Wood pellets | £1,578 | £0.084 | 0.6 |
| Mains gas | £1,580 | £0.084 | 3.8 |
| Logs | £1,647 | £0.088 | 0.5 |
| Heating oil | £1,658 | £0.088 | 5.6 |
| Heat pump | £1,786 | £0.095 | 1.1 |
| Direct electric heating | £4,873 | £0.26 | 3.3 |
Energy prices verified as of 2026-01-01
Heat pump and solar panels
If you have or plan solar panels, some of the running cost is covered by your own generation. There is little of it in winter, though — so we calculate conservatively.
Go to the solar payback calculatorHeat pump tariff
Heat pump tariff — Specialist heat pump electricity tariff
Conditions: Several suppliers offer a discounted unit rate for households running a heat pump, usually requiring a smart meter and a certified installation. Rates and eligibility vary by supplier.
Heat pump tariffGrant
Boiler Upgrade Scheme
£7 500 towards an air source or ground source heat pump in England and Wales. Since 21 July 2026 a property heated by oil or LPG with no mains gas connection can get £9 000 towards an air source heat pump.
Scheme detailsThis calculation is indicative and based on the values you enter plus average parameters for the UK (climate data, energy prices, installation costs). Actual consumption and savings depend on the specific property, the hydraulics, the controls and the installer. It does not replace a heat loss survey or an installer's quote.
How heat pump payback is calculated
The calculation runs in four steps. First the property's heat loss in kW is derived from the heated floor area and the building standard — the output the house needs on the coldest day of the year. Heat loss per square metre ranges from 15 W/m² for a passive house to 200 W/m² for an uninsulated older property, corrected for ceiling height, the design outdoor temperature of your region and any heat recovery ventilation.
From the heat loss and heating degree days we get the annual space heating demand, and add separately calculated hot water demand based on the number of occupants. The total is useful heat — the common denominator every heat source has to deliver, whether that is a gas boiler or a heat pump.
The heat pump's efficiency (SCOP) is not guessed but derived from the flow temperature and the type of heat pump. Underfloor heating at 35 °C gives a far higher SCOP than radiators at 55 °C — this is the single biggest lever in the whole calculation. The datasheet figure is then reduced to a realistic field efficiency and topped up with the share of heat the immersion heater supplies below the bivalent point.
Finally the annual cost of every source is put on the same amount of heat, the heat pump cost is subtracted from your current heating cost and the difference is compared with the investment less any grant. Electricity and fuel rise at different rates — and that difference is what the whole decision turns on.
Why the calculator does not ask for heat loss or SCOP
Most calculators on the market demand heat loss in kW and a SCOP figure in the very first field. Those are two numbers an ordinary homeowner has no way of knowing — and a blind guess ruins the whole result.
We derive them from things people do know: floor area, the age and condition of the property, and the type of heat emitters. If you know your heat loss from a survey, you can override it in advanced settings and the calculation will use that instead.
When a heat pump does not pay off
There are three situations where the calculator answers no. The first is an uninsulated property with old radiators needing water at around 65 °C — efficiency drops below 3 and the saving evaporates. The second is cheap current fuel: if you burn your own logs or have very cheap mains gas, electricity will not beat it per kWh of heat. The third is an investment that is simply too large for a small heat demand, typically in a small, well-insulated home.
The calculator says so plainly, with the reason. An honest answer matters more to us than pushing everyone into an enquiry form.
The Boiler Upgrade Scheme grant and the heat pump tariff
A grant reduces the net investment and therefore shortens payback, but it does not change the annual saving. Switch it on in the calculator and enter the amount you qualify for — we pre-fill an estimate based on the scheme's current rules.
A discounted electricity tariff, by contrast, changes the annual saving itself, and substantially. We include the higher standing charge that comes with it — without that the tariff would look better than it really is.
Frequently asked questions
What size heat pump do I need?
The required output comes from the property's heat loss plus an allowance for hot water. For a typical family home in the UK that is usually 6 to 12 kW. Air source units are sized slightly smaller because the peak on the coldest days is covered by the immersion heater — cheaper than an oversized unit that would cycle all winter.
What is SCOP and why does the calculator not ask for it?
SCOP is the seasonal coefficient of performance — how many kWh of heat the unit delivers from one kWh of electricity over a year. It depends mainly on flow temperature, so we derive it from whether you have underfloor heating or radiators. We also reduce the datasheet figure to real measured conditions.
Is a heat pump worth it instead of a gas boiler?
It depends on the ratio of electricity to gas prices and on the flow temperature your property needs. In a well-insulated home with underfloor heating, yes; in an uninsulated home with old radiators, usually not. The calculator compares both on the same amount of heat and gives a specific answer.
How is the hot water cost calculated?
From the number of occupants, daily use per person and the difference between cylinder temperature and incoming cold water temperature, including cylinder losses. Hot water has its own efficiency because it is always heated to a higher temperature than the heating water.
What is the bivalent point?
The outdoor temperature below which the heat pump's output is no longer enough and an immersion heater tops it up. The lower it is, the less electricity is used at an efficiency of 1 — but the larger and more expensive the unit has to be.
How accurate are the fuel prices?
Prices are verified as of the date shown under the result and come from published tariffs and averages. For coal, logs and pellets the regional spread is wide, so every price can be overridden in advanced settings.