Broad networks could also help ease one of renewable energy’s biggest problems: intermittency. When the wind drops in Britain, it may still be strong in Germany, or the sun may be shining in Tunisia. Households drawing power from a grid thousands of miles wide are less likely to be affected by the vagaries of any individual source’s output. That in turn means less need for expensive backup generating capacity from power plants that use natural gas or coal.

The Energy and Climate Change Committee of Britain’s main parliamentary chamber, the House of Commons, said in a report in September that a drastically improved grid would be crucial for the viability of the country’s plans for significant investment in offshore wind power.

For now, Britain “is virtually an energy island,” the report said, adding that the current approach of linking each offshore wind farm directly to land, rather than to a wider network, was costly and inefficient.

But the report listed several caveats about the development of a Europe-wide grid, saying the cost would probably be high and the challenge of coordinating national energy regulations would be daunting.

Tim Yeo, the committee’s Conservative chairman, said by phone recently that better connections would give the British energy industry access to big markets. It would also enable the country to make more use of wind power domestically by ensuring that imported power would be available in calm weather.

But he warned that the decades-long time frame for investing in energy infrastructure inevitably contrasted with the shorter-term focus of politicians.

Because energy is a heavily regulated sector, one of the biggest obstacles to building a supergrid is the long negotiations required to bridge differences among individual countries’ rules.