In our Southern California region, electric car chargers installed at home use an average of 10 kWh extra per night. When designing residential solar energy systems, we measure the monthly load. An additional 300 kilowatt hours of electric vehicles are added to the total electricity consumption. The average monthly load of desert households is about 1500 kilowatt hours, so we increased the load of electric vehicle chargers to 1800 kilowatt hours. Due to the fact that non electric vehicle households typically require at least 11 kilowatts of solar energy, this will increase the size of the solar cell array for households with electric vehicles to approximately 13 kilowatts. Adding four solar modules will provide additional power generation to offset the driving mode of people who use electric vehicles to travel 12000 miles per year.