Enter the floor area, ceiling height, insulation level and the gap between inside and outside temperature.
Formula
P (W) = Volume (m³) × G × ΔT, with G from 0.75 (very good insulation) to 1.6 (poor)
Worked example
80 m², 2.5 m high, good insulation, 25 °C difference: about 5,000 W.
Frequently asked questions
What temperature difference should I use?
Indoor 19–20 °C minus the coldest usual outdoor temperature in your area.
Is this enough to size a heat pump?
It is a first estimate; a professional heat-loss study is more precise.
Why does insulation matter so much?
Poor insulation can double the power needed.
Related calculators
Results are estimates for information only. Check important figures with a professional.