National Grid has reported a 45% jump in pre-tax profits to £938m in the first six months of the year.
The operator of the UK's electricity and gas networks said all its key operations performed strongly.
The big profits rise was helped by what the company said was a "significant" under-recovery of revenues last year.
But chief executive Steve Holliday said the results were very good, and that National Grid would continue to do well in the second half of the year.
"We expect to deliver strong operational and financial performance this year. We have made real progress on our priorities for 2010-11," he said.