RANCHO CORDOVA, Calif. - Gov. Arnold Schwarzenegger signed an executive order Tuesday giving California the nation's most aggressive alternative energy standards, requiring utilities to get a third of their power from renewable sources by 2020.

Schwarzenegger said the order signed at a solar field in a Sacramento suburb will reduce California's dependence on fossil fuels and help clean its air while creating a reliable power supply for a state with 38 million people.

It also will ensure that California remains a pioneer in clean energy, he said.