We have passed peak light bulb. The average amount of electricity needed annually to light a UK home fell from 720 kilowatt-hours in 1997 to 508 kWh in 2012, a drop of 29 per cent.

Brenda Boardman of the University of Oxford’s Environmental Change Institute says this is largely down to the phasing out of inefficient incandescent light bulbs. “Because of the amount we are switching to compact fluorescent light bulbs and LEDs, there is a huge drop in demand,” she says.

From 2007 to 2012, the UK’s peak electricity demand fell from 61.5 to 57.5 gigawatts. The benefits of efficient light bulbs are good news for the UK, which will have to work hard to maintain its electricity supply. Some of the nation’s ageing power stations are being mothballed over the next few years, while new capacity from renewable sources is slow in ramping up and planned nuclear reactors at Hinkley Point are a decade away. This means the risk of power shortages will rise in the next five years.

However, the switchover to energy-efficient light bulbs means any shortage would be unlikely to cause full-blown power cuts.


Keeping the lights on

Power shortages are most likely at times of peak electricity demand. In the UK and other countries in the northern hemisphere, this happens in December when people use more lighting due to the short days. The worst time is the early evening, when homes and offices are both lit. The electricity grid is designed with enough capacity to cope with this brief peak. “It’s the peak that determines the size of the whole system,” says Boardman. So anything that cuts the size of peak demand – such as low-energy light bulbs – reduces the risk of a power shortage.

“If there were ever a shortage at peak time, there would be power reductions,” says Boardman. In other words, the lights would dim but not go out. In extreme cases, a few big industrial complexes would be temporarily shut down to save power. But no homes or hospitals would find themselves in the dark, says Boardman: “Low-energy lights will keep the lights on.”

Boardman presented her work at the Radical Emission Reduction conference at the Royal Society in London in December.