We recommend 70 – 100 watts per square meter, depending on how well-insulated the building is. For larger rooms, it’s often advisable to use more than one heater, as long as the total wattage of the heater(s) is sufficient for the room size. A larger and more powerful heater will naturally heat up the room faster than a small heater with low wattage. If there isn’t enough wattage in a room, it will limit the maximum temperature achievable during the coldest months of the year.