Keeping both customers and shareholders happy is rarely easy for a power utility, as today’s full-year figures from Scotttish & Southern Energy demonstrate.

The £13 billion company has won plaudits from its customers for being the last of Britain’s six retail energy suppliers to increase its tarriffs - by some 15 per cent in March. That tactic has enabled it to swell its client base by 700,000 over the last year to secure 8.45 million domestic accounts, making it comfortably the country’s second biggest supplier behind Centrica.

The problem for shareholders is that surging energy prices this year - wholesale electricity and gas prices are up 31 per cent and 35 per cent respectively since March alone - means pulling in those new customers threatens to wipe out SSE’s supply profits this year. For that reason, the company is expected to have to raise its tarrifs by up to a further 15 per cent in September.

The flipside is that any earnings shortfall in supply could be made up by SSE’s generation business. Coal prices have risen less than gas prices - to which wholesale power prices are pegged - with the effect that profits from this division should surge.

SSE’s broader problem is that any perception in Westminster that utilities are profiting from high energy prices could bring a political backlash - and the spectre of windfall taxes.

But as long as SSE continues to invest heavily in its renewable energy portfolio to meet Government objectives - its total targeted spend over the next five years is £6.7 billion, nearly half of it on wind, hydro electricity and waste-to-power projects - that threat should be kept at bay.

However, those dynamics mean SSE’s shares - whose safe haven status enabled them to outperform the FTSE all share last year as the credit crunch hit - may find the going tougher from here.

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