You leave the living room, instinctively flipping the switch, convinced you are doing something for the planet and for your bill. This reflex of turning off the light when you leave a room has been taught since childhood, to the point of seeming unquestionable. Yet energy-saving specialists remind us that this gesture does not always have the imagined effect on the lifespan of bulbs and on real savings.
Nevertheless, everyone looks for simple ideas to ease their bill. EDF guides note that heating accounts for more than 60% of a home’s energy consumption, and lowering the thermostat by one degree can save about 7% on that item. Lighting, meanwhile, weighs in at roughly 10 to 15% depending on Engie. The real challenge then becomes less about turning everything off and more about turning off at the right moment, depending on the bulb and the duration of absence.
Turning off the light: a good reflex that depends on the bulb
Experts are clear: a bulb that is not needed should be switched off, but the gain depends on the type of lamp. LED bulbs, compact fluorescents, halogens, and incandescent lamps do not react the same way to repeated switch-ons. The myth that turning back on uses more energy than leaving it on is not true; the power spike at startup is very brief. In reality, the trade-off is mainly between energy saved and premature wear, especially for compact fluorescents.
For LEDs, studies cited by Okdiario remind us that they convert most of the electricity into light and consume up to 90% less than old incandescent bulbs. Their lifespan is around 25,000 hours, and turning them on and off often wears them very little. With this type of lamp, turning off the light when leaving, even for a few minutes, remains beneficial. The big lever remains replacing old bulbs with LEDs.
15-minute rule: when to switch off or leave on
Compact fluorescent lamps, or CFLs, offer about 85% efficiency and an average lifespan close to 8,000 hours, according to Okdiario. Their weakness lies in on-off cycles: too frequent turn-offs shorten their life. Specialists advise turning them off if the room stays empty for more than 15 minutes; below that, the energy benefit becomes small compared to accelerated wear. The startup energy spike hardly increases the bill.
For halogens and incandescent lamps, the reasoning changes again. They mainly convert electricity into heat and wear quickly, with only 750 to 2,000 hours of life according to Okdiario. A simple rule of thumb can help daily:
- LED: switch off as soon as the room is empty, even briefly.
- Compact fluorescent: switch off if the absence exceeds 15 minutes; otherwise tolerate turning on.
- Halogen or incandescent: switch off as soon as you leave, and plan a replacement with LED.
How to turn off the light without thinking about it: sensors and smart priorities
To avoid asking the question with every trip back and forth, motion detectors, timer switches, or presence sensors automatically cut lighting as soon as the room is empty. These solutions work well for hallways, toilets, laundry rooms, or cellars, where lights are often left on. Paired with LED bulbs, they limit waste without changing your habits.
Energy advisers remind that lighting remains a small item compared with heating, which accounts for more than 60% of a home’s consumption according to EDF. Optimizing the use of lights is useful, but the bulk of savings mostly comes from heating and replacing old bulbs.
