The "big six" energy firms made an average profit margin of 20 per cent for energy generation in their last financial year, according to figures released by energy regulator Ofgem.
The results are likely to fuel further anger over rising gas and electricity bills.
The key figures included:
- Profits in the domestic supply business increased by 75 per cent
- Companies made on average £53 per customer each year
- Average profit margins increased from 2.8 per cent to 4.3 per cent in 2012
- The big six made an average profit margin of 20 per cent for energy generation in the last financial year
More top news
President Barack Obama and First Lady Michelle Obama have celebrated Star Wars Day by getting down with R2-D2 and some storm troopers.
Police are appealing for information about two sisters aged 12 and five who went missing three days ago.
Senior medical staff have urged junior doctors and the Government to break the deadlock over the medics' long-running contract dispute.