Octopus Energy (Octopus) customers will receive a £50 annual saving to their energy bills.
This is part of a £50m package to ease household energy costs this year.
The saving will be a reduction to the raised price cap in April – with annual energy prices set to rise to nearly £2,000.
This follows market carnage across the domestic energy sector, which has seen nearly 30 suppliers go bust since August.
Octopus is now the UK’s fourth biggest energy supplier, and recently took on 580,000 customers from fallen firm Avro Energy.