RWE Npower saw its profits climb by 20 per cent in the six months to the end of June, rising to £2.91 billion despite revenues falling by one per cent.
The company said that part of its success was down to people locking-in to energy tariffs before wholesale gas and energy prices slumped during the downturn.
Large profits at RWE Npower may come as a warning to consumers, who could end up paying over the odds by fixing their tariffs for long periods of time.
It seems that using price comparison sites to track down the cheapest deals and regularly switching suppliers could be the best way for customers to save money.
Especially when RWE Npower has already claimed that whatever happens its full-year profits will be at least equal to or above last year's figures.
And with French energy firm EDF claiming that the cost of new nuclear power plants in the UK could push up energy prices for consumers, now could be a good time to consider switching.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.