The SNP administration found itself in a politically tight spot over nuclear power yesterday. Last year the party's energy review concluded that nuclear energy is no longer needed in Scotland. What a difference a year makes. Yesterday Scottish Energy Minister Jim Mather was quick to welcome the announcement that the lifetime of the Hunterston B power station in North Ayrshire is to be extended by five years, while insisting that Scotland does not need or want new nuclear stations.

The inconvenient truth for the Nationalists is that nuclear currently accounts for 40% of power generated in Scotland. As the world urgently seeks ways to cut emissions of carbon-dioxide and halt global warming, many believe it is the wrong moment to be contemplating ditching a major low-carbon energy source, despite the issues of reliability, decommissioning and the disposal of nuclear waste. It is true that Scotland offers the best potential in Europe for harnessing the power of wind and sea. And there are interesting developments in clean coal technology, including carbon capture and storage. But it will be years before these technologies are in a position to take up the slack from Hunterston, which was originally scheduled to close in 2011.

The most developed renewable is wind power and this week saw the announcement of a massive expansion in offshore capacity. But that will never be a substitute for nuclear because, while aerogenerators are good at providing low-carbon electricity, there is a problem on windless days. Nuclear, by contrast, can be relied upon to provide a constant base load. Hunterston's reprieve is welcome because it provides a vital breathing space while the government works out how to reconfigure generating capacity. It is also important to use this opportunity to improve Scotland's record on energy conservation and efficiency. For instance, the average household squanders £300 a year because of inadequate insulation and tougher standards are not enforced. The decision also gives the government more time to make key decisions about the next generation of nuclear power stations, though in all likelihood these would be built in England, near to where the power is needed, especially given the hostility of the SNP.

For now, the SNP government appears happy to send out mixed messages on nuclear power, even though a five-year extension for Hunterston means five extra years of nuclear waste to be disposed of. The public has yet to be convinced that Britain can manage without nuclear in the mix, not only because of fears about global warming but also as a result of looming energy insecurity. It is reasonable to ask whether we would not be better relying on our own nuclear generation than a European gas market dominated by the Russian giant Gazprom. Its former chairman, Dmitry Medvedev - the man who imposed big price rises on Russia's former Soviet neighbours - is now favourite to succeed Vladimir Putin. Yesterday's announcement buys us time to recalibrate Britain's energy capacity. There is an onus on ministers at Holyrood and Westminster to use it well.