Energy Cost Comparison Calculator
Compare heating fuels on a like-for-like cost per useful kWh.
Please note: An estimate based on the figures you entered. Real-world results vary with conditions this calculation cannot see, so treat it as a starting point rather than a final answer.
What the Energy Cost Comparison Calculator does
Comparing fuels by headline price is misleading because they carry different amounts of energy per unit and appliances convert them with different efficiency. Dividing price by both gives cost per useful kWh — the only figure that compares like for like.
Formula
Cost per useful kWh = Price per unit ÷ (Energy per unit × Appliance efficiency)Annual cost = Annual heat needed × Cost per useful kWhUnits needed = Annual heat ÷ (Energy per unit × Efficiency)
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Fuel A | one of 5 options | Yes | — |
| Price per unit of fuel A | selected currency | Yes | Accepts more than 0. |
| Appliance efficiency A | % | Yes | Resistive electric 100%, condensing boiler 90%, heat pump 300%+. |
| Fuel B | one of 5 options | Yes | — |
| Price per unit of fuel B | selected currency | Yes | Accepts more than 0. |
| Appliance efficiency B | % | Yes | — |
| Annual heat needed | kWh | Yes | Accepts more than 0. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Fuel A and Fuel B.
- Enter Price per unit of fuel A, Appliance efficiency A, Price per unit of fuel B and Appliance efficiency B and 1 more.
- Select Calculate.
Worked example
Electricity at $0.28/kWh with a 100% efficient heater versus gas at $0.90/m³ with a 90% boiler, for 12,000 kWh of heat.
- Fuel A
- Electricity 0.28
- Fuel B
- Gas 0.90
- Heat needed
- 12000
Electricity $0.28 per useful kWh ($3,360). Gas $0.0948 ($1,137). Gas is 2.95× cheaper, saving $2,223 a year.
Frequently asked questions
How can a heat pump be more than 100% efficient?
It moves heat rather than creating it. A coefficient of performance of 3 means three units of heat delivered per unit of electricity consumed — enter that as 300%.
Why does energy content matter?
A cubic metre of gas contains over ten times the energy of a kWh of electricity, so comparing their per-unit prices directly is meaningless.