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LED strings sip power: a whole season of a 200-bulb tree typically costs less than one mince pie. Timers (dusk till bedtime) do the maths automatically, and outdoor lights want an RCD-protected outdoor socket rather than a cable through the window.
What The Christmas Lights Cost Calculator Works Out
- Whole-season cost: watts divided by 1,000 x hours on per day x days lit, priced at the current Ofgem price cap unit rate. A 200-bulb LED tree string draws about 6W, so six hours a night across a forty-day season is 1.4 kWh, around 40p: less than one mince pie. Even ambitious multi-string house displays in the tens of watts run a few pounds.
- Per day: the season cost divided by the days lit. Power scales with bulb count and chip, not sparkle; twinkle modes and smart app-driven strings add negligible load.
- LED vs incandescent: the same tree string over the same season at 6W against the 40W incandescent sets LEDs replaced, which cost several times more and ran hot enough to scorch drying real trees.
- Unit rate, own wattage and number of sets (advanced): use your tariff's rate, a wattage read off the transformer label, and multiply for every set in the display.
- Per hour lit (advanced): the running cost per hour for the whole display, usually a fraction of a penny. The street's famous mega-displays, ten thousand LEDs and a sound system, still often run under a pound a night, which is why the neighbourly objection is glare, never the grid.
- Standby cost (advanced): what the controllers and transformers draw during the hours the lights are off, if left plugged in. Switching off at the plug or smart socket removes it.
- Switching one set to LED (advanced): the seasonal saving from replacing an incandescent set with an LED one, and how many seasons the new set takes to pay back, typically one or two.
- A timer would save (advanced): the cost of the hours a timer or smart plug would trim each day, holding the display to dusk till bedtime.
- Share of a December bill (advanced): the lights' kilowatt-hours against a typical home's 300 kWh December electricity. The genuinely expensive festive electricity is the oven's Christmas Day marathon and the extra fridge in the garage running all month. Outdoor displays want IP44-rated lights and connectors, an RCD on the circuit, transformers under cover, and cables through grommets or flat window cables rather than crushed in the sash.