Home Heating Energy Calculator

Home heating calculator

How much heat does your home need on a very cold day?

Start with a quick estimate in a few minutes. Then add more detail only if you want a tighter result.

Default design temperature −5°C You can change this

Step 1

Tell us the basics

No room-by-room measuring is needed for the first estimate.

⌂

Use your Energy Performance Certificate (EPC)

For now, please look up your property manually on the official GOV.UK EPC service, then copy the relevant information into this calculator.

Look up my property on GOV.UK

Automatic property lookup is coming soon. In a future version, you will be able to enter your address or postcode and have available EPC details filled in automatically.

Property name optional Postcode optional Total floor area

m²

Usually shown on your EPC. Property type Approximate age Number of storeys you heat Average indoor temperature

°C

Cold-day outdoor temperature

°C

−5°C is the default. Later we can suggest this automatically from postcode.

Step 2

Your quick estimate

This gives a useful starting range without making you measure every room.

Basic estimate

Estimated peak heat loss — at −5°C outdoors

Reasonable range — Use the refine step to narrow this down.

What this means

Walls & glazing—

Roof / ceiling—

Floor—

Air leakage / ventilation—

Don't buy a heat pump from this number alone. A final heat-pump design should use a proper room-by-room heat-loss calculation and the manufacturer's output at the required outdoor and water-flow temperatures.

What should I do next? Improve the estimate for a better result, or continue now to compare heating technologies.

Continue to Heating System Recommender →

Step 3 · Optional

Refine the estimate

Only answer what you know. The calculator keeps sensible defaults for everything else.

Refined estimate

Building height & shape

Measure the wall height once for each level — not every room.

Know the outside footprint dimensions? Optional. This improves wall-area accuracy.

Building length

Building width

Insulation & construction

External walls Windows Loft / roof insulation Ground floor How draughty does it feel? Approximate window area

Optional EPC cross-check

EPC space-heating demand optional

kWh/yr

This is used as a sense-check, not as the peak heat-loss calculation. EPC rating optional

Refined peak heat-loss estimate —

Indicative range —

Next step

Next: choose the best heating system for your home

Carry your calculated peak heat loss into the next questionnaire and rank the most suitable heat-pump technologies for your priorities.

Compare heating systems →

Want to continue another day? Create a free account and your home details can be saved.

Create account Log in

How the estimate works

The calculator estimates design heat loss from fabric losses (walls, glazing, roof and floor) plus ventilation/infiltration losses. The quick mode estimates geometry from floor area, storeys and property type. The refine mode lets the user replace those assumptions with better information.

It is intended to be a homeowner planning tool. Final heat-pump selection should still be checked with a room-by-room professional design calculation.