What are watts, kilowatts, and kilowatt-hours?
The size of a solar electric system is often described in watts (W) or kilowatts (kW). One kW = 1,000 W. Watts are a unit of power, just like the horsepower of an engine. They express the maximum possible output of energy the system can produce at any point in time. When sunlight strikes solar electric panels, they produce electricity that is measured in kilowatt hours (kWh). Kilowatt hours are the units of energy you buy from your utility and use in your home to run your appliances, lighting and electronics. In Oregon, a good rule of thumb is that 1,000 watts of solar electric panels require about 100 square-feet of space and will typically produce 1,000-1,300 kWh of electricity each year. If you double or triple the size of the system, you will double or triple the amount of electricity it produces.
