THE lights are on but no one is home at the Worcester headquarters of energy provider npower – just days after the firm announced price rises affecting thousands of households.

Pictured at 7pm on Monday evening, lights at the building, in Warndon, were burning brightly long after most workers had left for home.

This week, the firm announced a 9.3 per cent rise in electricity prices, and an 11.1 per cent rise in the cost of gas. A duel-fuel bill would increase by 10.4 per cent, it said.

The company claimed the lights could have been set off by security staff, or by staff who “often work late into the night”, but the sight angered npower customer John Sadford, who lives in Warndon.

“It’s an absolute joke that they can jack up everyone’s energy bill while lighting up their own office like a Christmas tree, when virtually no one is there,” said Mr Sadford, aged 30.

“It’s a kick in the teeth for customers, like me, who already struggle to make ends meet.”

But an npower spokesman said there could have been reasons behind the lights being on.

He said: “Npower is one of a few major energy suppliers to be awarded the Carbon Trust Standard for reducing its impact on the environment year-on-year.

“All our lighting systems operate via a passive infrared system which is triggered by movement. We have security guards on site who regularly patrol our offices.

“In addition our hard-working staff often work late into the night.”

The price rises announced by npower come into force on Sunday, December 1, affecting 3.1 million customers across the UK.

Announcing the increased charges, npower chief executive, Paul Massara, said: “I know that any increases to household bills are always unwelcome and this is not a decision that we have taken lightly.

"We will continue to take steps where we can to reduce the impact of the external influences on energy bills.”