Heat Pumps · Flagship calculator
Heat Pump Savings Calculator
Compare the annual running cost of a heat pump with your current gas, oil, LPG or direct-electric heating for the same useful heat, then see simple payback and the change in emissions. Starting values are examples — replace them with your own bills, tariff, SCOP and quote.
Your home & heating
Heat delivered into the home, not fuel bought. Example value — replace with your own, or start from last year's fuel use.
Example value — use the unit rate on your bill.
Example value — real seasonal efficiency of your boiler or heater, often below its rated figure.
Example value — use your tariff for the hours the heat pump runs.
Example value — the seasonal rating for your climate and flow temperature, not a single-point COP. COP vs SCOP
After any grants. Example value — use your quote.
0.177 is the UK Government 2025 grid factor (generation only). Replace with your grid's. Choosing a factor
Estimated annual running-cost difference
€467
Estimated lower running cost than natural gas at these inputs.
Simple payback — full installed cost
25.7 years
€12,000 ÷ annual saving. Ignores maintenance, financing, price changes and discounting.
Estimated CO₂e change / year
2,291 kg lower
Current: 3,049 kg · heat pump: 759 kg. Fuel factor 0.18296 kg CO₂e/kWh (gross CV), combustion only, from the UK Government 2025 conversion factors (UK fuels).
€1,667/yr
€1,200/yr
15,000 kWh
16,667 kWh
4,286 kWh
SCOP above 2.52, or electricity below €0.389/kWh
Fuel price per kWh used: 0.10.
How the calculation works
useful heat = fuel used × kWh per unit × efficiency (or entered directly)
current cost = useful heat ÷ efficiency ÷ kWh per unit × fuel price
heat pump cost = useful heat ÷ SCOP × electricity price
annual difference = current cost − heat pump cost
simple payback = upfront cost ÷ annual difference (only if positive)
break-even SCOP = efficiency × electricity price ÷ fuel price per kWh
Both systems are compared on the same useful heat. Because the existing system's efficiency is part of the comparison, the break-even condition is not simply "price ratio below SCOP": the electricity-to-fuel price ratio must be below SCOP ÷ existing efficiency.
Oil and LPG energy content (kWh per litre, gross CV) and the fuel emission factors come from the UK Government 2025 conversion factors for UK fuels; other countries' fuels can differ slightly. All prices, efficiencies, SCOP, heat demand and cost are example values. The heat pump savings and payback guide works through the same method; constants and sources are on the calculation methodology page.