Determining Calorifier Size

calorifier or calefaction = heater.

This depends on the difference between the inside and out side temperatures. Are you in a tropical country? How are the walls and windows insulated? is it a modern building.

All these you need to know to allow you yo calculate the heater required to warm a room with ?insulation and ?outside temperature.

Most portable heaters are 1000 to 1500 watts

according to my heat consumption for this year, just for heating, the maximum power required was of about 200-250 W/m2. I have to mention that this was in winter time, having having about -6 to -10 deg C average temperature, and -28 deg C for about a week. Now outside the temperature is between -1 and 7 deg C and the daily electrical energy consumption is of about 10 kWh/day for an area of 12 m2; this leads to about 35 W/m2 average power. The wall is reinforced concrete and brick, about 30 cm thick. no exterior or interior insulation. The windows are PVC framing with double layered glass 1 cm apart from each other. the outside wall is about 9 m2. hope it helps