Cost comparison
| Metric | Current system | Heat pump |
|---|---|---|
| Annual cost | £1,200 | £980 |
| Energy input | 16,026 kWh | 4,541 kWh electricity |
| CO₂ emissions | 2,566 kg | 940 kg |
Annual savings / extra cost
£220 cheaper
10-year projection
£2,200 lower energy spend
Narrative summary
Methodology
Formulas and assumptions
If you enter an annual bill, the calculator first converts that cost into annual fuel input using the selected tariff. For gas, oil, and LPG systems, useful heat delivered is then estimated by multiplying fuel input by your chosen system efficiency. For direct electric systems, efficiency is treated as 100%.
Heat pump running cost is calculated as useful heat demand divided by SCOP, then multiplied by the electricity tariff. Carbon emissions use UK-focused factors: gas 0.203 kg/kWh, electricity 0.207 kg/kWh, oil 0.247 kg/kWh, and LPG 0.214 kg/kWh.
Oil is converted from pence per litre to pence per kWh using an approximate energy content of 10 kWh per litre. The 10-year comparison is a straight-line projection that keeps today’s tariffs and system efficiency constant, so it is best used as a comparison baseline rather than a market forecast.
This tool covers space-heating energy only. It does not include standing charges, maintenance, capital cost, cylinder losses, or future tariff changes. Those should be considered separately when making a full investment decision.