Sizing guide

Heater wattage by room

Most small bedrooms can often cope with around 750W to 1,000W, while average living rooms often need more like 1,500W to 2,000W. These are only starting points, but they help you avoid wildly mismatched heater choices.

Last reviewed: 16 April 2026 - Room examples for UK homes

Room typeTypical starting pointWhy it can change
Box bedroom750W to 1,000WPoor glazing or external walls can push the need higher.
Medium bedroom / office1,000W to 1,500WCold-start heating and higher ceilings increase the requirement.
Average living room1,500W to 2,000WLarge windows, exposed walls and open-plan layouts push this up.
Large cold room2,000W plusAt this point, room fabric and the heating approach matter as much as the heater size.