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Enter how much heat your home needs per year, the efficiency of the heat pump (seasonal performance factor) and the prices. You see the electricity the heat pump needs, its cost, the cost with your boiler, and the difference.

Enter your values

From your gas bill (kWh), or about 10 kWh per litre of heating oil.
Where do I find this?

Look at your last yearly gas bill: the consumption in kWh is a good estimate. If it shows m³, use the Gas m³ to kWh Calculator.

For heating oil, one litre is roughly 10 kWh. These figures include the losses of the old boiler, so the heat actually needed is a little lower: multiply by your boiler efficiency if you want to be exact.

Heat delivered per kWh of electricity over a year. Often 3 to 4 for air, 4 to 5 for ground source.
Where do I find this?

The Jahresarbeitszahl (JAZ) is the yearly heat output divided by the yearly electricity input. Your installer or the data sheet gives an estimate for your house.

A lower flow temperature, for example with underfloor heating, gives a higher value. 3.5 is an example.

Per kWh. Heat pump tariffs are often cheaper than normal household tariffs.
Where do I find this?

Use the price per kWh of your heat pump or household tariff from the contract or bill. 25 ct = 0.25.

Per kWh of gas. Use the oil price per kWh if you heat with oil.
Where do I find this?

Look for 'Arbeitspreis' or 'price per kWh' on your gas bill. For oil, divide the price per litre by about 10.

Share of the fuel that becomes heat. Often 80 to 95 %.
Where do I find this?

The boiler's data sheet or the chimney sweep's report states it. Older boilers are lower, modern condensing boilers higher. 90 is an example.

Only changes the symbol; no exchange rate is applied.

Result

Enter your values to see the result.

Heat pump saves per year
– (negative = costs more)
Heat pump cost per year
–
Boiler cost per year
–
Heat pump electricity
– kWh
Boiler fuel
– kWh

Want this tracked for you? UtilityControl logs your meters and costs automatically.

How it is calculated

  • Heat pump electricity (kWh) = heat demand ÷ seasonal performance factor
  • Boiler fuel (kWh) = heat demand ÷ (boiler efficiency ÷ 100)
  • Cost = kWh × price per kWh; saving = boiler cost − heat pump cost

Example

15,000 kWh of heat with a factor of 3.5 needs 4,286 kWh of electricity: 1,071 at 0.25. The old boiler at 90 % needs 16,667 kWh of gas: 1,667 at 0.10. The heat pump saves about 595 a year.

What this estimate leaves out

The result depends strongly on the real performance factor, which depends on the house and the flow temperature. Investment, grants, maintenance and price changes are not included.

Written and reviewed by QLines, Cologne · Last reviewed

Read the PV and heat pump planning guide (German)

FAQ

Frequently Asked Questions

How much electricity does a heat pump use?

Divide the yearly heat demand by the seasonal performance factor. A house needing 15,000 kWh of heat with a factor of 3.5 uses about 4,300 kWh of electricity a year.

What is the Jahresarbeitszahl (JAZ)?

The seasonal performance factor: the heat the heat pump delivers over a year divided by the electricity it uses. A value of 4 means one kWh of electricity gives four kWh of heat. Air-source pumps are often around 3 to 4, ground-source around 4 to 5.

Is a heat pump cheaper to run than a gas boiler?

Often yes when the performance factor is good and the electricity price is not far above three times the gas price. Enter your own prices to see it for your house.

Where do I find my heat demand?

On your last yearly gas bill, in kWh. For oil, a litre is about 10 kWh. A heating engineer can calculate it more precisely.

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