EDF Energy’s chief executive has insisted Sizewell C must be part of the UK’s future energy mix.

Simone Rossi told a Westminster energy sector summit that nuclear needed to be included to deliver the minimum level of demand on the electrical grid.

He said the UK needed nuclear to generate a base load “regardless of whether the sun is shining or the wind is blowing”.

Addressing this year’s Utility Week Energy Summit, Mr Rossi also suggested Suffolk’s proposed third nuclear plant would be “much cheaper” than the £19.6bn Hinkley Point C in Somerset.

Alex Chisholm, permanent secretary of the Department of Energy and Climate Change, opened with UK’s energy policy, before Ofgem chief Dermot Nolan looked at the future energy in the UK, making way for Mr Rossi to state the case for new nuclear.

He told the summit: “To decarbonise the electricity system, we need to bring our carbon down to 60grams per KWh – it is 220g at the moment.

“We support as much wind as practically possible, but wind alone is not reliable. There are extra costs when there’s not enough, or too much wind, and that cost gets higher the more you decarbonise the system.

“Solar can contribute something in the UK but it is not a very good match to demand. It does almost nothing in winter evenings when the demand is highest.”

Days earlier, Summit Power claimed its new Scottish gas plant, with carbon capture and storage (CCS), could generate electricity with a lower strike price than Hinkley Point C.

Mr Rossi told the summit: “Gas cannot be the only backup because it’s not low carbon and CCS isn’t ready.”

He said Sizewell C could deliver power in a cost effective way, with a grid connection largely in place and close proximity to major electricity demand centres, avoiding need for deep National Grid reinforcement.

He said construction could be 20% cheaper than Hinkley Point C because the design was largely identical and the workforce was mobilised and trained.

“Nuclear needs to be competitive with other low carbon generation, which we know it can be, through the series benefits of using technology that is up and running, making it an attractive asset for the private investment the government wants to see in new nuclear projects,” he concluded.