How Many Watts Does Your Room Need

Outside district heating, the first question is always "how powerful should it be". The rule of thumb is 100W per square metre: 1500W for 15㎡, 2500W for 25㎡.

Rooms are not laboratories though. Ceilings above 2.8m, poor insulation or full-height glazing add 20–30%. A mid-floor, south-facing, well-sealed room can drop a step.

One thing is usually missed: wattage decides whether it gets warm, airflow decides how fast. At the same 2000W, a convector warms the whole room evenly but slowly; a fan heater gives hot air in three seconds but only in one direction.