The site — 175 hectares, or about 430 acres — is just south of a 1970s-era nuclear station known as Hinkley Point B, which is operated by EDF. And looming over the fields are the eerie, boxy shells of two 1960s-era reactors that have been shut down for more than a decade but still employ a couple of hundred people in the decommissioning.

EDF executives say they have already spent £1 billion, or about $1.5 billion, getting to the “shovel-ready” point for the reactors. After years of study, Britain’s nuclear and environmental regulators have approved designs, and about 70 percent of the necessary contracts are already lined up and ready to be signed. If and when the new plant, Hinkley Point C, comes fully online, it will supply about 7 percent of Britain’s electricity. That would be enough power to meet the needs of five million homes, with the added benefit of no carbon emissions.

On Tuesday, Edward Davey, Britain’s energy and climate change minister, is expected to announce the final decision on whether Hinkley Point construction can begin. It would be a moot point, though, if EDF did not agree to proceed.

The sticking point has been what electricity price the government will guarantee. It has vowed not to subsidize new nuclear power plants. But energy legislation now wending through Parliament includes a means to set a floor price for the electricity from the new plants, with customers covering the cost.

With the price tag for the Hinkley Point plant estimated at £14 billion, or $21 billion, EDF is thought to be seeking a floor price of around £100 per megawatt-hour — about double the current rate for electricity in Britain. That is what EDF would need to earn the 10 percent return on investment that it is looking for, according to estimates by Harold Hutchinson, an analyst at Investec in London. The British government is thought to be pushing for something closer to an 8 percent rate of return.

EDF Energy is already one of the biggest utility companies in Britain, and the former prime minister Tony Blair used to say that a French utility’s providing energy for his Downing Street office was proof of the openness of the British economy. But the current government might fear the political beating it would take if it were perceived to be guaranteeing high profits to a French company.

Just how much the price supports would add to household electric bills is hard to gauge. The government has said that various new clean-energy measures to support nuclear energy, as well as wind and solar power, will add about 4 percent to the average household electric bill by 2020.