It’s the 21st Century and Britain’s energy customers are more vulnerable than ever.

Read our round-up of how five different energy companies responded to the changes.

On Monday, Ofgem, the energy regulator, set out plans to cap gas and electricity bills for almost 11 million households.

The measure comes as a result of a drop in wholesale prices, a boost to energy efficiency programs and warnings from major supermarkets that they could take over smaller suppliers and hike prices. The cost of supplying the average dual fuel customer with electricity and gas costs suppliers £1,101 per year, Ofgem estimates.

Some of Britain’s leading energy companies — the big six — responded to the cap by claiming they wouldn’t be affected.

But consumer groups claimed that while they haven’t been asked, they’d be surprised if the threat to undercut prices with a cheaper deal is held over anyone who’s already on a cap.

Rival consumer groups said more needs to be done to protect customers from rising energy bills, which can put pressure on household budgets.

The government also defended its decision to set a cap on bills — and said households will see a £25 (about €30) a year decrease in their energy bills in the first year alone.