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A heat pump should match the heating load of the building. Enter the heated area and pick the standard of the building. You get a rough load in kW and a likely range, which is a good starting point for talking to an installer.

Enter your values

Floor area of the rooms that are heated.
Where do I find this?

Use the heated living area from the plans or the energy certificate. Unheated cellars and attics do not count.

Pick the closest match. Better insulation means a smaller heat pump.
Where do I find this?

New buildings and well-insulated houses need the least heat per m². Houses built before the 1990s without renovation need the most.

These W/m² values are common rules of thumb, not a measurement. The energy certificate or a heating load calculation (DIN EN 12831) gives the exact value.

Result

Enter your values to see the result.

Estimated heating load
– kW
Likely range, from
– kW
Likely range, to
– kW

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How it is calculated

  • Heating load (kW) = heated area (m²) × heat demand per m² (W/m²) ÷ 1000
  • Likely range = load − 20 % to load + 20 %

Example

A partly renovated house with 150 m² heated area: 150 × 80 ÷ 1000 = 12 kW, with a likely range of 9.6 to 14.4 kW.

What this estimate leaves out

This is only a rule-of-thumb estimate. Hot water, the building's insulation, the climate and how many people live there change the real value. Always have a heating load calculation done before you choose a heat pump.

Written and reviewed by QLines, Cologne · Last reviewed

Read the PV and heat pump planning guide (German)

FAQ

Frequently Asked Questions

What size heat pump do I need?

The heat pump should cover the heating load of the building. A first estimate is the heated area times about 50 W/m² for a new or well-insulated house, 80 for a partly renovated one and 120 for an old, unrenovated one. A heating engineer confirms it with a proper calculation.

Is a bigger heat pump better?

No. An oversized heat pump switches on and off often, which wastes energy and wears it out. It should fit the load.

How do I find the exact heating load?

Ask a heating engineer for a heating load calculation (Heizlastberechnung, DIN EN 12831) for your house. Your energy certificate and last gas or oil bills are useful inputs.

Does hot water count?

Yes, a little: it adds a small amount to the load. This quick estimate does not include it, so leave room when you choose the size.

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