For many Christmas revellers, fairy lights on the fir tree are a winter staple.

But incandescent lightbulbs could add £20 to energy bills according to one energy supplier.

In comparison it would cost just 18 pence to power some brands of low energy LED fairy lights, said Good Energy.

The supplier worked out the energy use of an ‘average’ set of Christmas tree lights based on DECC’s 2013 estimate for the average price of electricity of 13.49p per kilowatt hour (KWh).

They multiplied this for a Christmas period from the first day of December until the twelfth night of Christmas (the 6th of January), or 37 days, assuming the lights were switched on for an average of six hours a day.

Juliet Davenport, founder and CEO of Good Energy said: “It’s surprising how much electricity Christmas lights use up. Switching to LED lights will save you money and is good for the environment.”

Find a full breakdown of how the supplier calculated the lights’ cost is here.