Short answer: at the current Ofgem price cap - 26.32p per kWh, in force from October to December 2026 - a typical all-LED display costs under £5 for the whole of December. One LED string costs about 34p for the month, roughly a penny a night. Only displays still using old incandescent sets can reach £10-30. Here is the full breakdown in pounds and pence - and the free Christmas Lights Cost Calculator now has a £ mode that works out your own display.
The two numbers on your bill that matter
Your electricity bill has a standing charge (54.83p a day at the cap) and a unit rate (26.32p per kWh). The standing charge is the same whether you run one string of lights or a thousand - your decorations cannot change it, so ignore it for this question. Everything your lights add comes through the unit rate alone: watts × hours ÷ 1,000 × 26.32p. That is why the honest UK figures are so much smaller than the scare stories - and why switching tariffs or suppliers changes your lights’ cost by pennies, not pounds.
What each light costs in December (UK table)
Six hours a night for the 31 nights of December, at the capped unit rate of 26.32p per kWh:
| Type of light | Watts | Cost for December |
|---|---|---|
| LED string, 100 lights | about 7 W | about 34p |
| LED C9 string, 25 bulbs | about 15 W | about 73p |
| Incandescent mini string, 100 lights | about 40 W | about £1.96 |
| Incandescent C9 string, 25 big bulbs | 175 W | about £8.57 |
| Inflatable (UK fan-and-LED kind) | about 24 W | about £1.17 |
| LED projector | about 7 W | about 34p |
These match the figures UK sources publish: Which? puts one LED string at about 44p across the longer stretch from December into mid-January, and a typical combined house display - strings, net lights, icicles - at under £5 for December. A worked example: 8 LED strings, an inflatable and a projector draw about 87 watts; over December at 6 hours a night that is 16.2 kWh, about £4.26.
LED vs old bulbs, in pounds
The gap is the same as everywhere, just priced in pence: an old C9 string costs about £8.57 for December against 34p for an LED string - twenty-five times as much, for the same corner of the roof. A house running ten old mini strings pays about £19.60 for December where the LED house pays about £3.40. If anything on your house still glows warm and gets warmer, that is where your December money is going.
Inflatables in the UK: smaller fans, same trap
UK inflatables are usually a modest fan-and-LED affair of about 24 watts - nothing like the 150-300-watt American kind - and cost about £1.17 across December at six hours a night. The trap is identical though: leave it running around the clock and the same inflatable costs about £4.68, quietly becoming the most expensive item in the display. A timer set for the hours people are actually outside - roughly 4 to 10 p.m. is the common UK pattern - keeps it at the £1 figure.
Work out your own display in pounds
The Christmas Lights Cost Calculator counts your display string by string; select £ at the top and it fills in the current price-cap rate for you (you can type your own tariff’s unit rate if you are not on the cap). It shows the December total, the per-night cost, and what the same display would cost with the old strings swapped for LED. Reading from the US, or buying lights as gifts across the pond? The main guide - How Much Does It Cost to Run Christmas Lights? - has the same breakdown in dollars.
Three ways to pay less, keeping every light
Timer everything. Six hours instead of ten cuts the running cost by 40%, and UK streets are quiet long before midnight. Retire the hottest strings. Old C9 and mini sets are nearly all of the wattage in a mixed display; replacing only those brings the bill down to LED levels. Check your unit rate once. If you are on a fixed tariff above the cap, your lights cost proportionally more than the tables here - the calculator takes your real rate. And one comfort: at LED wattages, your display costs less across the whole of December than cooking Christmas dinner does on the day.
Frequently asked questions
How much do Christmas lights cost to run in the UK?
At the October-December 2026 price cap of 26.32p per kWh, a typical all-LED display costs under £5 for the whole of December. One LED string is about 34p for the month. Displays still using old incandescent sets can reach £10-30.
How much do Christmas lights cost per day in the UK?
About a penny a day for an LED string (roughly 1.1p at 6 hours a night), and about £4-5 spread across the month - call it 15p a day - for a whole typical LED display. An old C9 string alone is about 28p a day.
Do Christmas lights add a lot to the electricity bill?
LED ones do not: a whole display adds less across December than one day of oven cooking. The additions that show up are old incandescent strings (one C9 set is £8.57 for December) and anything left running around the clock.
Do Christmas lights affect the standing charge?
No. The standing charge - 54.83p a day at the current cap - is fixed and identical whether you decorate or not. Lights only add usage at your unit rate, which is why their cost is measured in pence.
Is it cheaper to run Christmas lights on a timer in the UK?
Yes, exactly in proportion to the hours saved. Six hours a night instead of ten cuts the cost by 40%; the typical UK pattern of about six hours an evening is already the economical one.