Christmas lights (LED) and energy costs - could be better, could be worse ......... 19 September 2022 at 1:05PM in Energy 21 replies 1.5K views

GustyGardenGalaxy

A bit of reading reveals that some councils aren't going to be switching on their town/city Christmas lights this year due to the rising energy costs.

This of course got me thinking - how much will it cost for somebody to have a few Christmas lights at home, on the tree for example?

Must be LED lights of course as they use around 10% of the energy of the older incandescent lights.

Based on the government's figures:

https://www.gov.uk/government/publications/energy-bills-support/energy-bills-support-factsheet-8-september-2022

and using the standard variable tariff of 34p kWh I estimate that it could cost about £1.20 to run 200 LED bulbs (0.1W per bulb) for six hours.

Does this seem reasonable or am I way off with my calculations?

Another solution is to perhaps use some of those short strings of lights that are powered by AA or AAA batteries, and of course to use rechargeable batteries (which don't seem to cost much to recharge).

Any thoughts?

[Deleted User]

Batteries would not be a useful idea - charging a battery to power something takes a little more energy than just powering the thing directly.

A string of 100 LED xmas tree lights uses about 4W from what I can see.  1 kWh of electricity would, therefore, power the string for 1000/4 or 250 hours.

That makes the single string of tree lights cost 34p for nearly 10 1/2 days.


edit: here's the power supply from my xmas tree lights - 3.6W

Miser1964

Most lights have some on/off settings for chase, flash, slo-glo etc. which would reduce consumption over steady on. 

GustyGardenGalaxy

Deleted_User said:

Batteries would not be a useful idea - charging a battery to power something takes a little more energy than just powering the thing directly.

A string of 100 LED xmas tree lights uses about 4W from what I can see.  1 kWh of electricity would, therefore, power the string for 1000/4 or 250 hours.

That makes the single string of tree lights cost 34p for nearly 10 1/2 days.


edit: here's the power supply from my xmas tree lights - 3.6W

Thanks, that's far better than I thought.

I guess another option would be fiber optic displays using a single LED bulb - they can look good at even less cost.

[Deleted User]

The same maths will work for anything.  Find out its continuous (or average) power use in Watts (W), then divide 1000 by that number and it tells you how many hours it will work for 1 unit (or for 34p).

markin

Under 10 watts you have to use 0.01W

[Deleted User]

markin said:

Under 10 watts you have to use 0.01W

No.  For 10 watts you would use 0.01kW.  0.01W is one-hundredth of a watt.

Magnitio

GustyGardenGalaxy said:

and using the standard variable tariff of 34p kWh I estimate that it could cost about £1.20 to run 200 LED bulbs (0.1W per bulb) for six hours.

Does this seem reasonable or am I way off with my calculations?

200 LED bulbs each rated at 0.1W =20W.

20W for 6 hours = 120Wh.

120Wh at 34p/kWh = 120/1000 * 34 = 4p.

So, if you have them on for 3 weeks, that is 3*7*4= 84p.

I'll leave you to judge whether you were way off.

Grizzlebeard

At Christmas, assume it will be chilly, then turn down your central heating by one tenth of a degree^^ and you will save enough energy to power your LED lights 24/7 for 10 years.

^^Difficult to do, and made up guestimate figures - but you get the idea.

Miser1964

Or cook the sprouts for 5 minutes less, the savings will pay for the Xmas lights. 

otb666

when doing calculations i always like to compare to one 100w lightbulb which uses one unit of electric in 10 hours So for 20w you get 50 hours for one unit of electric As i only put tree lights on a few evenings during xmas week  this one units will cost me 28p