The government has given the go-ahead for the UK's first new nuclear station in a generation.
France's EDF Energy will lead a consortium, which includes Chinese investors, to build the Hinkley Point C plant in Somerset.
Ministers say the deal will help take the UK towards low-carbon power and lower generating costs in future.
Critics warn guaranteeing the group a price for electricity at twice the current level will raise bills.
"For the first time, a nuclear station in this country will not have been built with money from the British taxpayer," said Secretary of State for Energy Edward Davey.
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If the electricity price is below the strike price, then bills will probably go up. If it is above the strike price, then bills could go down.”
Q&A: Nuclear strike price
The two reactors planned for Hinkley, which will provide power for about 60 years, are a key part of the coalition's drive to shift the UK away from fossil fuels towards low-carbon power.
Ministers and EDF have been in talks for more than a year about the minimum price the company will be paid for electricity produced at the site, which the government estimates will cost £16bn to build.
The two sides have now agreed the "strike price" of £92.50 for every megawatt hour of energy Hinkley C generates. This is almost twice the current wholesale cost of electricity.