June marked two huge milestones in renewable energy in the U.S., with Hawaii and Vermont both passing laws that put in place the nation’s most ambitious renewable energy goals.

Electricity generation is the nation’s largest emitter of climate-changing greenhouse gases, leading many states to set goals for how much of their power should come from low-carbon renewable energy. Today, 29 states have laws mandating a certain portion of their power to be generated from renewables as a way to combat climate change, but none have gone so far as Hawaii and Vermont.

When Hawaii Gov. David Ige signed the state’s renewable energy bill into law on June 8, the Aloha State became the first in the U.S. to mandate all of its electricity come from renewables. The goal must be met by 2045 not only as a way to reduce Hawaii’s contribution to greenhouse gas emissions, but also to reduce the cost of the state’s electricity.

Vermont followed Hawaii on June 11 with what may be an even more ambitious goal — to generate 75 percent of the state’s electricity from renewables by 2032, with 55 percent coming from renewables by 2017, less than two years from now.

Overall, the U.S. is a mosaic of commitments to renewable energy. More than half the states have some goal to boost renewables as a way to shrink their carbon footprints. California, Maine and New York, for instance, each have a mandate for at least 30 percent of their power to come from renewables. But other states take a different tack. Kansas rescinded its renewables mandate earlier this year, turning it into a voluntary goal. States such as Florida, Idaho, Wyoming and Georgia have no renewables mandate at all.

Those states stand to learn from more ambitious states, and sometimes follow their lead when it comes to climate policy. Such was the case with Hawaii, which announced its intent to pass a 100 percent renewables mandate shortly after California Gov. Jerry Brown declared that his state should revise its renewables goal from 33 percent by 2020 to 50 percent by 2030, said Peter Shattuck, clean energy director for the Acadia Center, a Boston-based think tank focusing on energy and climate change.

“Every state doing something more ambitious fundamentally expands the realm of the possible,” he said. “I think at the highest level, what Vermont and Hawaii stand to show is how quickly renewables are becoming competitive sources of energy.”

Renewables are already a major part of how electricity is generated in both Hawaii and Vermont, which, in addition to being small in size and population, are unique in several ways.

Hawaii, isolated in the Pacific Ocean, has the nation’s highest electric power rates because it generates 93 percent of its electricity using imported crude oil brought there by ship. The high rates have spawned a rush of rooftop solar panel installations across the islands, where 12 percent of all homes have solar cells on their roofs — more than any other state.

On the opposite side of the country, Vermont is unique for different reasons. The state found itself in a bind last year after it lost 70 percent of its electric power generation when the Vermont Yankee Nuclear Power Plant shut down in December. The closure forced the state to get most of its electricity from the New England electric grid, which is powered using mostly natural gas.