BOSTON — Gov. Deval Patrick’s administration has set a new goal for solar energy installations in Massachusetts after reaching its initial target four years early.

Patrick said the state’s new goal will be 1,600 megawatts of solar energy by the year 2020. That would generate enough electricity to power 240,000 homes per year and reduce greenhouse gas emissions by the equivalent of 166,000 cars.

The governor and other state officials said on Wednesday that with the help of solar energy incentives offered by the state, Massachusetts had already reached a goal of installing 250 megawatts of solar power by 2017. That is enough to power for 37,000 homes.

Officials also cited a report from the Solar Energy Industries Association that residential solar electricity prices fell 28 percent in Massachusetts last year.