Heater Power kW by Room Area

Sizing electric heater power by area

As a rough guide, figure around 100 W/m² for a well-insulated room in a mild climate, climbing to 150–200 W/m² where it gets cold and the insulation is poor. Take a 15 m² bedroom in Gramado in winter, with roughly a 5 °C indoor target swing: 15 × 150 = 2,250 W (2.25 kW), which puts a 2,000–2,400 W heater in the right range. Dial the factor down for double-glazed windows and solid insulation, and push it up for high ceilings, single-pane glass, or drafts.

Applications

You see this a lot in the Serra Gaúcha (Gramado, Canela), in Campos do Jordão where winter dips to −1 °C, across the Serra Catarinense, and in apartments with no central heating. As for the heaters themselves: convection is fast but dries the air, infrared / quartz is radiant and warms objects directly, oil-filled runs silent and holds its heat, and gas puts out a lot of power but needs ventilation. Check the breaker capacity first, since a 2 kW heater on 127 V pulls about 16 A.

FAQ

Is 100 W/m² always enough? Only when the climate is mild and the insulation is good. Up in the southern Brazilian highlands, count on 150 W/m² or more.

Oil or convection heater — which? For a bedroom, oil-filled wins on safety and quiet. Convection warms the room faster, but it dries the air out.

Does ceiling height matter? It does. Once you go above 2.8 m, add 10–15 % for each extra meter, because there's more air to heat.