By using the thumb rule, you can easily determine the coverage area of any power wattage. 150 sq ft can be covered by (150 sq ft x10) 1500 watts. Similarly,300 sq ft, 500 sq ft, and 600 sq ft of the area can easily heat up by 3000, 5000, and 6000 watts. These values may differ due to some other factors like insulated areas or too many windows or openings in the place where the heater is installed.