Retail operating profits at SSE rose by nearly 40% to £456.8 million in the last year.
The huge rise in earnings to the end of March 2015 comes despite the supplier losing more than 500,000 customers during the same period.
The Big Six company blamed “increasingly challenging and highly competitive market conditions” for the fall to 8.5 million accounts.
The rise in profits follows a hike in energy prices in November 2013.
Adjusted profit before tax rose by 0.9% to £1.5 billion but wholesale operating profits fell by 25.3% to £473.8 million due to “tough market conditions and lower output”.
The company also confirmed it will close its Ferrybridge coal power station by March next year while the Fiddler’s Ferry plant in Lancashire will be entered into the Capacity Market auction at the end of 2015.
Chief Executive Alistair Phillips-Davies said: “It’s been a challenging year with some difficult decisions being made but it is a year in which we have continued to deliver for customers. In a very competitive market we’ve cut prices twice in 13 months and extended our price guarantee which will mean SSE customers will have seen no increases for at least two and a half years.”
The company cut its gas prices by 4.1% last month and promised to freeze them until next year.
SSE’s networks business saw profits rise 1.8% to £936.8 million “reflecting the continuing major investment in the infrastructure”.
It has invested more than £800 million since 2013 and expects to invest around £600 million in 2015/16.