WASHINGTON—Gov. Jay Inslee proposed Friday that the U.S. should require carbon-neutral power by 2030, laying out a climate plan at the start of his presidential campaign that embraces elements of the Green New Deal, which many Democrats have backed.

The Washington state governor, who has made climate change central to his long-shot bid for the White House, said that if elected he would set targets for achieving 100% clean energy across the electrical grid and in new vehicles and buildings.

The plan, which didn’t include a cost assessment, would put the nation on a path to have all renewable and zero-emission energy in electrical generation by 2035.

“There is a dark cloud over America and that is the dark cloud of climate change caused by carbon pollution that is an existential threat to the people of the United States,” Mr. Inslee said at a news conference in Los Angeles with the city’s mayor, Eric Garcetti, who considered a 2020 presidential campaign but decided not to run.

Environmental policy has taken on a new urgency in the Democratic primaries, pushed along by a report from a United Nations-led scientific panel last fall that said nations around the world needed to take drastic steps to limit global warming to avoid catastrophic climate change.