The size of your optimal solar array will be influenced by many variables. Before analyzing those variables, you should understand how solar is sized and measured. The electrical capacity of solar panels is measured in watts (W). The typical solar panel is rated at 250-300 W. To get the total power (in watts) of your solar array, add together the wattages of each panel. Let’s say you had 10 300 W panels installed. The total wattage of your system would equal 3,000 W. 1,000 W is equal to 1 kilowatt (kW), so another way to describe the size of that system would be 3 kW. The average size of a solar array is 5 kW.