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While I think it is really nice to see people's Christmas lights throughout the festive season, I imagine that it must be really bad for the environment. How much energy do they use and are there alternatives?
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A watt (W) is a unit of measurement of power. Today, this information appears on the technical descriptions for all electrical appliances1 kilowatt (kW) = 1,000 watts (W).

1 kilowatt hour (kWh) is the energy consumed by a 1,000W or 1kW electrical appliance operating for 1 hour.

So in order to calculate the energy consumed by an appliance, you would multiply its power (in KW) by the number of hours it runs.

 

According to the Centre for Global Development (CDG), decorative seasonal lights account for 6.6 billion kWh of electricity consumption every year in the United States, which could run 14 million refrigerators and is more than the annual electricity consumption of many developing countries.

 

Christmas lights at home (figures from Which?):

Christmas lights are on for about 30 days, 6 hours every night, making it about 180 hours during the season.

A string of 100 incandescent fairy lights has a power of 40W.

This brings energy consumption of a fairy light for the season to about 7kWh.

A household uses 7 strings on an average, consuming about 50kWh.

To get an approximate comparison, a 1000W microwave oven, operating for 1.5 hours/week, consumes 60kWh in a year.

An average outdoor Christmas lighting display consumes 12.5 times more energy than a string of 160 incandescent fairy lights.

 

Christmas lights on the high street (figures from energuide.be):

On an average, Christmas lights are on from early December until mid-January, for about 8 hours every night, and some nights until the morning, making it about 330 hours during the season.

A traditional chain of lights with incandescent bulbs has a power of between 600W to decorate an average street and 1,500W for a major route.

This brings total consumption to between about 200 and 500kWh, an average of about 350kWh.

Lighting up a large Christmas tree uses 1,000W, which makes its consumption 330kWh.

The total for the season for a high street would be about 680kWh. An inefficient combi fridge-freezer (energy rating C) switched on throughout the year uses less than that at 500kWh.

 

Energy can be saved by turning Christmas lights off before bed.

If the incandescent lights are replaced by LED lights, it can reduce energy consumption by 90%!

 

References:

https://www.which.co.uk/news/2017/12/how-much-are-your-christmas-lights-going-to-cost-you/

https://www.energuide.be/en/questions-answers/what-do-watt-and-kwh-mean/121/

https://www.energuide.be/en/questions-answers/who-takes-care-of-the-christmas-lights-and-how-much-power-do-they-actually-use/186/

https://www.energuide.be/en/questions-answers/how-much-energy-do-my-household-appliances-use/71/

https://www.cgdev.org/blog/us-holiday-lights-use-more-electricity-el-salvador-does-year

https://www.researchgate.net/publication/263969440_The_Carbon_Cost_of_Christmas

by (470 points)
edited ago by
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Christmas lights can consume a lot of energy; a typical string of 100 small incandescent bulbs requires 40 Watts, while their LED equivalent only around 5 Watts.

There are a number of ways you can reduce your Carbon footprint:

1. Only keep lights on when necessary or consider putting them on a timer to limit energy usage

2. Use LEDs; they use less energy, are cheaper to run and tend to last longer

3. Use solar powered lights. These are by now widely available for prices which are more or less comparable to standard lights which require mains electricity.

You can find out more about the energy consumption of different lights at https://www.christmasdesigners.com/blog/much-electricity-led-christmas-lights-use/

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