If you've still got halogen downlights, you're paying for light you're not getting. A 50W halogen GU10 and a 5W LED GU10 can produce a similar amount of usable light — the halogen just wastes the other 45W as heat. This guide walks through the real numbers for a UK home, using UK average electricity prices.
The Quick Comparison
Here's what a typical swap looks like for 10 downlights, run 4 hours a day, every day, at the UK average electricity rate of £0.245/kWh:
| 50W Halogen | 5W LED | |
|---|---|---|
| Total wattage (10 bulbs) | 500W | 50W |
| Annual energy use | 728 kWh | 73 kWh |
| Annual running cost | £178.36 | £17.84 |
Annual saving: £160.52 — a 90% reduction in running cost, just from swapping the bulbs. At around £1.38 per LED GU10 replacement, the whole set of 10 bulbs costs under £14 — meaning it pays for itself in the electricity saving within the first month.
Why the Difference Is So Large
Halogen bulbs create light by heating a filament — most of the electricity goes into heat, not light. LEDs produce light directly, so far less energy is wasted. That's why a 5W LED can match the brightness of a 50W halogen: it isn't doing 10x less work, it's just not throwing 90% of the energy away as heat.
It's Not Just the Electricity Bill
Halogen bulbs also fail far more often. A typical halogen GU10 lasts around 2,000 hours; a good LED lasts 25,000 hours or more — over 12x longer. For 10 bulbs run 4 hours a day, that's the difference between replacing halogens roughly 3 times a year versus an LED set lasting the better part of a decade. Fewer replacements means less time on a stepladder and less spent on bulbs, on top of the electricity saving above.
Check Your Own Numbers
Every room is different — more bulbs, different hours, a different current bulb type. Rather than guess, use our free energy savings calculator to plug in your actual setup and see your real annual saving, payback time, and CO₂ reduction.
Which LED Should You Buy?
If your current fitting takes a GU10 bulb, a straight swap is usually all you need — no rewiring required. Our GU10 LED bulbs range covers warm white, cool white, and dimmable options. If you're not sure which base your downlight takes, our GU10 vs MR16 vs MR11 vs GU11 guide will help you identify it before you order.