With LEDs, Is Daylight Saving Still Meant to Save Energy—and Do We Need It?

Why the clocks changed

The UK adopted summer time in 1916, during the first world war, aiming to conserve fuel and improve productivity. Moving clocks forward was expected to reduce the need for artificial light after sunset.

LEDs transform lighting use

Incandescent bulbs wasted much of their electricity as heat, converting only about 5% to 10% into light. They were phased out in the UK between 2009 and 2012; most halogen bulbs, which use similar technology, followed in 2021.

LEDs are now the most efficient bulbs in widespread use. A 13.5-watt LED produces about 1,520 lumens, comparable to a 100-watt incandescent bulb, using around 86% less electricity. As a result, producing the same amount of artificial light now takes much less power.

Savings remain uncertain

The 2026 House of Commons Library report found the effect of clock changes on energy demand inconclusive. Reduced use of lighting may be offset by shifts in heating and cooling demand.

Energy use has also changed

Lighting made up about 4% of UK household electricity use in 2025, or roughly 1% of total household energy use, including gas for heating, according to government estimates. Overall household energy consumption has generally fallen since the 2000s, mainly because of other efficiency measures.

Cheaper-to-run lights may also lead people to use more of them, including for decoration, or leave them on longer. This rebound effect is one reason researchers must consider the wider energy system, alongside changes such as renewable energy, electric cars and increased use of electronic equipment.

Europe has not settled the issue

LEDs have weakened one original reason for changing the clocks, but the evidence does not show that lighting efficiency alone determines the overall energy impact. Whether the practice still saves energy remains uncertain.