Storm Diana brought travel chaos to road, rail and airports, but the clouds did have a silver lining: the strong winds helped set a renewable energy record.

Windfarms supplied about a third of the UK’s electricity between 6pm and 6.30pm on Wednesday, a time of peak energy demand. Output hit a high of 14.9GW, beating a previous record of 14.5GW.

The milestone coincides with the official opening on Friday of E.ON’s Rampion windfarm off the coast near Brighton, which is the first in the Channel and can power about 350,000 homes.

Blustery weather has buoyed wind output in the past few days, with National Grid reporting thousands of wind turbines were the UK’s No 1 source of power across Wednesday and Thursday, at about 32% of generation. Gas power stations are usually top.

Windfarms have moved from a niche source of electricity generation a decade ago – when they supplied less than 2% – to a cornerstone of Britain’s power mix, at nearly 15% of supply last year.

The 400MW Rampion project is one of four big offshore windfarms to come online this year, along with a 92MW windfarm in Aberdeen Bay, a 353MW windfarm off the Suffolk coast and a 659MW windfarm off Cumbria, which is the world’s biggest.

More vast schemes are in the wings, with a 588MW windfarm in the Moray Firth due to become fully operational next year. The title of world’s largest windfarm will be taken by a 1,218MW project off east Yorkshire a year later.

Emma Pinchbeck, the executive director of the industry body RenewableUK, said: “It’s great to see British wind power setting new records at one of the coldest, darkest, wettest times of the year.”

Onshore windfarms are cheaper and provide more power than those offshore, but the government has blocked them from competing for subsidies

Consumers are being forced to pay higher energy bills thanks to the cost of installing smart meters – and things could still get worse, according to the spending watchdog.

An investigation by the National Audit Office (NAO) into the £11bn roll-out of the meters has suggested that energy bills could rise by more than £500m in total. It criticised the Government for allowing so many first-generation meters, which can “go dumb” after a switch of supplier, to be installed.

The costs of the roll-out are being added to energy bills and work out at around £374 per dual-fuel household. While there are said to be long-term benefits of having a smart meter, with the annual saving estimated at £18 a year by 2030, the NAO said the roll-out had had a negative impact on consumers’ bills so far.

The watchdog also warned that the savings estimates were based on the current budget for the roll-out. They do not factor in any cost increases if, say, first-generation meters need to be replaced. The Government’s bill-cutting estimates also assume that the industry passes on savings to consumers.

Lily Green of Look After My Bills, a switching service, said: “The smart meter roll-out has been an utter shambles. The endless delays, technical flaws and underestimating of costs to the taxpayer are no way to instill confidence in people that smart meters are a good choice.”

Claire Perry, the energy minister, described the roll-out as “world leading” and said it would bring benefits worth £40bn to consumers and the industry.

Smart meter rollout