Electric Room Heating Calculator

How to use this calculator

1. Enter the room's floor area in m² and the ceiling height.
2. Pick the insulation level (or enter a custom W/m²).
3. Click Estimate heating power for the total watts and a panel-heater suggestion.

How the estimate works

Comfort heating is commonly sized from a heat-load density in watts per square metre, then scaled for ceiling height:

The W/m² figure depends mainly on insulation. This is a rule-of-thumb for sizing room heaters — a full heat-loss calculation accounts for the climate zone, window area and ventilation.

Heat-load density by insulation

Bathrooms and rooms with large windows sit at the higher end of each band.

Frequently asked questions

How many watts to heat a room?

A well-insulated modern room needs roughly 40 W/m²; an average room 50–70 W/m²; an older, poorly insulated room can need 100 W/m² or more. Multiply by the floor area.

How many panel heaters do I need?

Divide the total watts among heaters so each room has at least one, sized in common steps (e.g. 400, 600, 800, 1000 W). Two smaller heaters often give more even heat than one large one.

Is this the same as a heat-loss calculation?

No. This is a quick rule-of-thumb for sizing heaters. A formal heat-loss (EN 12831) calculation accounts for climate, orientation, windows and air changes.