The extreme heat this summer has been unrelenting in many parts of the country.

With higher temperatures also comes higher demand for electricity to power air-conditioning units, fans and dehumidifiers as people try to stay cool. That’s all putting strain on power plants and the electric grid, which further heats up the planet.

Nuclear power, however, is totally free of carbon emissions. And on Monday, a new reactor at a nuclear power plant in Georgia came online — the nation’s first new reactor to be built from scratch in decades.

The reactor at Plant Vogtle is the first of two new units at the plant, ultimately capable of powering half a million homes in Georgia, Florida and Alabama. But the project is seven years behind schedule and more than double the projected cost — to the tune of almost $35 billion.

“The challenge is this is really a first-of-a-kind project. And I know that sounds weird because we — the U.S. does have so much nuclear. It’s 20% of our electricity,” said Jessica Lovering, executive director of Good Energy Collective, which advocates for nuclear energy. “But the U.S. industry really kind of closed down or was in a cold shutdown for 30 years. We weren’t building new projects.”

That’s partly because of incidents like the Fukushima disaster in Japan, which underscored the technology’s safety risks, but also because building these plants is really expensive.

So even when fossil fuel prices went up, nuclear often wasn’t an attractive option, according to Isabella Alcañiz, who teaches government and politics at the University of Maryland.

“Now, climate change, global warming seem to offer another window of opportunity,” she said. “But again, the big issues of safety and cost keep being an obstacle.”

Who exactly bears those costs will be the big issue moving forward, said Tim Echols of Georgia’s Public Service Commission. Plant Vogtle has been a passion project of his.

While Echols said he’s glad it’s up and running, “I don’t know that I would enter into doing this again without a financial backstop from the federal government that says these reactors will not cost you any more than X, no matter what.”

Echols said plant owners and equipment manufacturers had to eat some of the cost overruns, but utility customers will also see their electricity bills go up about $5 a month as soon as this week.