How Much Do LED Bulbs Save? UK Halogen to LED Savings
Swapping one 50 W halogen spotlight for a 5 W LED saves about £13.30 a year if the light is on 3 hours a day and your unit rate is 27p per kWh, because the LED uses 90% less energy. A kitchen or bathroom ceiling with 20 spotlights saves £266.09 a year, and at £3.00 a bulb the LEDs pay for themselves in about 2.7 months. The LED bulb savings calculator works it out for your own bulbs, hours and unit rate.
How to work out what an LED saves
- Find the watts saved per bulb: 50 W − 5 W = 45 W.
- Turn it into kWh a year: 45 W × 3 hours × 365 days ÷ 1,000 = 49.3 kWh.
- Multiply by your unit rate: 49.3 kWh × 27p = £13.30 a year for one bulb.
- Multiply by the number of bulbs: 20 bulbs save 985.5 kWh, or £266.09 a year (£22.17 a month).
- Work out the payback: 20 LEDs at £3.00 cost £60.00; £60.00 ÷ £22.17 a month = 2.7 months.
The same spotlight costs £14.78 a year to run as a halogen and £1.48 as an LED. Use the unit rate in pence per kWh from your bill, not the standing charge: the standing charge is a daily fee and does not change when you change the bulbs.
Saving per bulb by brightness
Compare lumens, not watts. Brightness in lumens, the incandescent bulb it replaces and the range of LED watts in the US Department of Energy FEMP table (lumens are the same unit in the UK). Saving per bulb per year at 3 hours a day and 27p per kWh.
| Brightness | Old incandescent | LED watts | Saving per bulb per year |
|---|---|---|---|
| 450 lumens | 40 W | 4.5 to 7.0 W | £9.76 to £10.50 |
| 800 lumens | 60 W | 5.9 to 10.5 W | £14.63 to £15.99 |
| 1,100 lumens | 75 W | 9.5 to 14.0 W | £18.03 to £19.37 |
| 1,600 lumens | 100 W | 10.5 to 18.0 W | £24.24 to £26.46 |
Check the cap on the old bulb before you buy: B22 bayonet, E27 or E14 screw, or GU10 for spotlights. If the light is on a dimmer, buy LEDs marked dimmable.
Saving by hours a day
One 50 W halogen replaced by a 5 W LED at 27p per kWh, with the LED at £3.00. Change the bulbs that are on longest first: kitchen, living room and outside lights.
| Hours on | Energy saved per year | Saving per year | Payback |
|---|---|---|---|
| 1 h a day | 16.4 kWh | £4.43 | 8.1 months |
| 2 h a day | 32.9 kWh | £8.87 | 4.1 months |
| 3 h a day | 49.3 kWh | £13.30 | 2.7 months |
| 4 h a day | 65.7 kWh | £17.74 | 2.0 months |
| 6 h a day | 98.6 kWh | £26.61 | 1.4 months |
| 8 h a day | 131.4 kWh | £35.48 | 1.0 months |
| 12 h a day | 197.1 kWh | £53.22 | 0.7 months |
Saving by unit rate
20 spotlights changed from 50 W to 5 W, on 3 hours a day, with LEDs at £3.00 each. Unit rates change with each price cap and tariff, so read across from yours.
| Unit rate | Saving per year | Saving per month | Payback |
|---|---|---|---|
| 20p per kWh | £197.10 | £16.43 | 3.7 months |
| 24p per kWh | £236.52 | £19.71 | 3.0 months |
| 27p per kWh | £266.09 | £22.17 | 2.7 months |
| 30p per kWh | £295.65 | £24.64 | 2.4 months |
| 35p per kWh | £344.93 | £28.74 | 2.1 months |
What changes the saving
- The old bulb. GU10 halogen spotlights are often 35 or 50 W; a 35 W one swapped for a 5 W LED saves £8.87 a year at the same hours and rate. Old incandescent bulbs of 40, 60 or 100 W save more. Enter the watts printed on the bulb you have.
- The hours. A bulb on 1 hour a day saves £4.43 a year and pays back in 8.1 months; a landing light that is rarely on can wait until it fails.
- Heat. Halogen bulbs turn most of their energy into heat, so in winter a little of the saving comes back as extra heating.
- Life. LED lamps are rated for many thousands of hours, far longer than halogens, so you also buy fewer bulbs. The rating is on the box.
For the rest of the house see how much it costs to run common appliances, or work out any device with the electricity cost calculator. Fairy lights are in the cost to run Christmas lights.
Frequently asked questions
How much does one LED bulb save per year?
About £13.30 a year for a 5 W LED that replaces a 50 W halogen, on 3 hours a day at 27p per kWh. That is 49.3 kWh a year. On 6 hours a day it is £26.61.
How much does a 50 W halogen spotlight cost to run?
At 3 hours a day and 27p per kWh, £14.78 a year. A 5 W LED spotlight costs £1.48.
How long do LED bulbs take to pay for themselves?
At £3.00 a bulb, 3 hours a day and 27p per kWh, about 2.7 months. A bulb on only 1 hour a day takes 8.1 months.
Does switching to LED lower my standing charge?
No. The standing charge is a fixed daily fee. LED bulbs cut the kWh you use, so the saving shows up in the unit-rate part of the bill.
Is it worth replacing halogen spotlights that still work?
For lights that are on a few hours a day, yes: an LED pays for itself within 2.7 months at 3 hours a day and then keeps saving. For lights that are rarely on, replace them when they fail.
More guides
Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and check the Building Regulations and any planning rules for anything structural or close to a boundary.
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