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The never-off lights

Easy · 6 min

💡 by user: Ivo Simonic · 🤖 Built & fact-checked by AI · ✅ Human approved

Modern daytime running lights never really switch off: they wake up with the engine and burn every kilometre, day and night, in most of the world. Nobody notices them — but there are billions of them, working without a break.

The never-off lights
AI illustration, house style

The question — as asked by Ivo Simonic

How much fuel do all the world's vehicles — cars, trucks, motorcycles — burn every day just to keep their daytime lights on?

In the proposer’s own words (untouched) — Ivo Simonic

quanto carburante consumano ogni giorno tutti gli automezzi, camion, automobili, moto, solamente per tenere accese le luci durante il giorno? trova il numero mondiale di automezzi circolanti, il consumo delle lampadine (luci di posizione anteriori e posteriori e anabaglianti) e fai la moltiplicazione. aggiungi anche il consumo effettivo in KW/h giorno

Work it out

  1. The fleet: about 1.64 billion cars on Earth (January 2025), plus vans, trucks and motorcycles — call it ~2 billion vehicles with lit lamps.
  2. The lamps: modern LED daytime running lights draw 5–20 watts (older halogen setups exceeded 110 W); since 2011 the EU forces low-power systems, so ~30 W per vehicle is a fair fleet average.
  3. The electric bill: 2 billion × 30 W × ~1 hour of driving a day = 60 million kWh every day — the electricity a whole country the size of Slovakia (~74 GWh/day) uses.
  4. The catch: lamps don't run on magic — the engine makes that electricity through an alternator at roughly 15% overall (alternator ~60% × engine ~25%). Divide by 0.15 and the bill becomes ~400 GWh a day of fuel.
  5. Fuel carries about 9 kWh per litre → about 45 million litres burned every single day (honest range: 30–67 million, depending on wattage and hours).
  6. In oil terms: ≈ 280,000 barrels a day — about 0.3% of all the oil the planet pumps — and roughly 18 Olympic swimming pools full of fuel, every single day.

What it teaches

One bulb is nothing; a fleet of two billion is everything. Europe didn't ban daytime lights — it capped their watts (headlamp-based DRLs were so wasteful they were outlawed in 2011). When a number is huge because it's a multiplication, you attack any factor you like — and the cheapest factor to attack is almost always the wattage, not the cars.

💡 Hermi's tip — make it yours

Look up your own car's DRL wattage (or measured amps × 12 V at the battery), your real daily driving hours, and re-run the chain: how many litres per year do YOUR lights cost?

✍️ From a reader’s idea

Proposed by: mdrnjackova · P20261108-172049-18ae · 2026-11-08

The original idea, word for word:

quanto carburante consumano ogni giorno tutti gli automezzi, camion, automobili, moto, solamente per tenere accese le luci durante il giorno? trova il numero mondiale di automezzi circolanti, il consumo delle lampadine (luci di posizione anteriori e posteriori e anabaglianti) e fai la moltiplicazione. aggiungi anche il consumo effettivo in KW/h giorno

Verified numbers behind it

How this page was built

🔌 this page, illustration and short took ≈35 Wh of compute to build — about 2 phone charges; the site's whole library costs less than one hour of an electric kettle