More than one million UK households will be refunded £10.4 million after an energy watchdog found 18 energy suppliers had overcharged customers when they switched to better deals.

Ofgem said suppliers including the Big Six firms such as British Gas, npower and EDF overcharged customers £7.2 million over seven years after failing to follow price protection rules.

The rules are designed to safeguard a customer’s tariff price when they decide to either switch suppliers or deals after a price increase.

It said several suppliers self-reported the issue to the regulator, which then prompted it to ask all firms to assess their practices, revealing failures among 18 suppliers between 2013 and 2020.

Which suppliers have to pay compensation?

This is the full list of suppliers that have to pay compensation - including how many customers have been affected and total redress package:

  • Bristol Energy: 12,617, £56,552.64
  • British Gas: 141,415, £1,269,095.47
  • E: 20,870, £72,772.93
  • E.On: 28,126, £238,884.29
  • EDF: 79,083, £516,191.55
  • Engie: 9,061, £21,218.74
  • ESB Energy: 1,961, £49,787.00
  • Green Star: 79,083, £808,351.00
  • Energy npower: 2,030, £25,602.69
  • Octopus Energy: 19,712, £121,444.52
  • Orbit: 723, £7,081.12
  • OVO Energy 240,563 £2,801,231.51
  • PFP Energy 5,347 £50,929.31
  • Scottish Power 157,236 £1,967,465.28
  • Shell 225,823 £1,217,203.40
  • So Energy 10,514 £78,480.89
  • SSE 132,620 £983,334.45
  • Utility Warehouse 2,723 £95,512.15

What customers were affected?

Ofgem says that in total, over one million customers were overcharged over £7.2 million.

The customers affected included:

  • Those on a standard variable tariff who switched to another supplier but did not have their variable tariff price protected during the switch
  • Customers on a fixed term tariff who switched to another supplier but did not have their fixed term tariff protected during the switch
  • Customers on a fixed term tariff who moved to another tariff with their supplier, but did not have their fixed term tariff protected during the switch

According to Ofgem, most of the failures were down to suppliers “not having adequate arrangements in place to make sure the protections were applied in full when customers divided to switch”.

The suppliers have since agreed to refund affected customers, and in some cases make goodwill payments, to the cost of £10.4 million.

Where it is not possible to process a refund, the suppliers have agreed to make payments to the energy redress fund.

Suppliers will get in contact with customers to arrange a refund - if you think you are owed a refund and haven’t heard anything, you should get in touch with your supplier.

‘Sending a strong message to all suppliers’

Anna Rossington, interim director of retail at Ofgem, said: “Customers should have confidence in switching and not be overcharged when doing so.

“This case sends a strong message to all suppliers that Ofgem will intervene where customers are overcharged and ensure that no supplier benefits from non-compliance.

“It also shows that, where appropriate, Ofgem is prepared to work with suppliers who have failed to comply with the rules, but who are willing to self-report issues and put thing right for their customers.”