Electricity Savings Can Vary
How much you actually save in electricity also depends on your location, how energy efficient your home is and what other changes you make to improve your home's energy efficiency.
Solar power works best in an energy efficient building, the Department of Energy says, so adding insulation, energy efficient lighting, appliances and windows goes far to reduce your home’s electricity use before you install your system.
Net Measuring a Local Benefit
Some utility companies use a measurement system called net metering, which could add to your savings.
With net metering, when your photovoltaic system generates more power than you need, the excess energy you create goes back to the grid and makes your meter run backward, in effect paying you for the energy you contribute.
For example, in Hawaii and New York, where retail electric rates are high, this could be especially beneficial, the Department of Energy says. And utility companies also benefit. The solar energy you’d provide would likely come during periods of peak demand for electricity, during the day.