To gain a significant rise in the air temperature in a room, your heater will need to circulate the volume of air in the room roughly 5 times per hour. That means this heater is suitable for rooms approx 5m by 5m by 3m or 75M3. These figures are based on a very well insulated room and doors kept closed. If in doubt always buy a larger capacity heater as air volume, ambient temperature and heat loss all play a part in setting your room temperature.