A couple years ago, I decided it would be interesting to find out about how much it was costing me to run my Christmas lights during the holiday season. The calculation is quite simple so I'll walk you through it. Some information you need to find out ahead of time:

1. How many bulbs you put up.
2. How often you typically have them turned on.
3. The cost for a kilowatt-hour from your power company. (should be listed on your bill)

And now for a little background information. A typical mini-bulb Christmas light uses about 0.5 watts per bulb. If you have LED bulbs or the large, old-school bulbs, you'd have to find out how many watts per bulb you ware using.

Let's assume that you put up 3,000 lights (on your tree, house, bushes, etc), and that you typically have them on from 5:00PM till 11:00PM from Dec 1 to Jan 14. Let's also assume that your electric company charges you $0.10 per kilowatt-hour (kWh).

So, here we go.

3,000 lights * 0.5 watts = 1,500 watts when they are all on.

1,500 watts / 1000 = 1.5 kilowatts. So, if you have all of them on for 1 hours, you have 1.5 kilowatt-hours.

1.5 kilowatt-hours * 6 hours per day = 9 kilowatt-hours per day.

9 kilowatt-hours per day * 45 days = 405 kilowatt-hours total usage by Christmas lights during the holiday season.

405 kilowatt-hours * $0.10 per kilowatt-hour = $40.50 to run your lights for the entire season.

You can see that this is no small chunk of change. Might make you consider switching to LED Christmas lights which will use only a tenth of the electricity because they are so efficient (they're also nearly indestructible).



As a side note, this calculation can be used for anything that you know the energy use of. For example, four 60 watt bulbs left on for about 3 hours per day. Or an 1100 watt oven cooking for 2 hours. Some of it will make you sick to see how much you are spending to operate that device.