Britain's power infrastructure is on the brink of what may be its biggest transformation. Underinvestment in the network for decades mean that a big overhaul is long overdue, but the changes are being accelerated by a string of other influences.

Tough new European Union pollution rules mean that nine of Britain's biggest coal and oil-fired power stations are due to be retired from service in 2015, while a string of other ageing nuclear stations built in the 1960s and 1970s are being decommissioned at the same time. Together, these plants represent about 25 per cent of UK power-generating capacity. They are the steady workhorses of Britain's energy system that have churned out heat and light to millions of homes for decades.

To avoid future supply disruptions and blackouts, they need to be replaced urgently — yet in an era of growing alarm over climate change and energy security, there is much debate over what should take their place. The industry has pledged to build a fleet of new nuclear power stations, but the first of these will not be ready before 2017, at the earliest.

At the same time, Britain has signed up to an ambitious EU plan to generate 35 per cent of its electricity from renewable energy, such as wind and wave power, by 2020 — a dramatic increase from today's figure of less than 5per cent.

Many in the industry doubt that this target is achievable, given the funding and planning wrangles faced by the wind developers and the complexity of linking schemes to the National Grid. Nevertheless, the Government is pushing hard for as many of these schemes to be built as possible.

Meanwhile, a host of new gas-fired power stations is also on the way. The share of Britain's electricity produced by burning gas has already risen from 2 per cent in 1992 to 35 per cent. The figure is expected to rise further, with gas-fired plants under construction at Pembroke in West Wales, the Isle of Grain in Kent and Langage, outside Plymouth.

Cheap and relatively quick to build, they may emit carbon but tend not to stoke the public ire against new coal plants. However, they do raise other problems. With domestic supplies of North Sea gas being depleted fast, the UK is becoming increasingly reliant on imports of the fuel from countries such as Russia, Qatar and Algeria, a trend that has raised concern about UK energy security.

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