Girl decorating a lit Christmas tree in a semi-lit festively decorated room - used for the National Grid story 'The Christmas 'energy effect' revealed'

ESO: The Christmas ‘energy effect’ revealed

Just how much do all those Christmas tree lights and turkeys baking in ovens boost Britain’s electricity use? Was it Strictly Come Dancing, Call the Midwife or the Queen’s Speech that caused the biggest pickup in power demand last Christmas? And do we use more or less energy on the 25th than normal? Roisin Quinn, our Head of National Control, explains all in our Christmas Q&A.

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Portrait photograph of Roisin Quinn - used in the National Grid article 'The Christmas 'energy effect' revealed'

Is the 25th busier or quieter than usual when it comes to electricity use?

Christmas Day is actually a time when electricity use is at one of its lowest points of the year. The cause for this fall in demand during Christmas is simple … over the festive period, schools, offices, shops and factories tend to be closed.

It may not be a white Christmas, but is it a green one?

We Brits love talking about the weather and we’re no different in the Electricity System Operator control room, as it has a big impact on demand for electricity and how green that power is too. Last Christmas, zero carbon sources generated 35% of electricity and, if it’s mild and blustery, we expect similar figures this year, perhaps even more.

Are more renewable sources used now than in previous years? How has this changed over time?

Just as the overall electricity system is changing, Christmas is changing too. Back in 2009, 23% of Christmas Day electricity was generated by coal – last year it was less than 4%. And it’s renewable or low-carbon sources that are making up the difference. Festive electricity sourced from wind power has risen from 0.3% in 2008 to 11% in 2018.

The greenest Christmas to date was 2016, as weather conditions and market factors meant the last two were slightly ‘higher carbon’. The question is: will 2019 be the greenest yet?

Graph showing percentage of generation mix between coal, low carbon and renewables over Christmas from 2009 to 2018 - used for the National Grid story 'The Christmas 'energy effect' revealed'

When is the peak demand for electricity?

It could be argued that the people of Great Britain are very much creatures of habit. Electricity demand usually rises as we get up and go to school or work. It plateaus throughout the day and then peaks at dinner time, when we get home. But at Christmas, the normal pattern of electricity use is a bit different. On Christmas Day the peak occurs earlier, at lunchtime, as we switch on our ovens and cook our Christmas feast. For example, on 25 December 2018, peak demand was for 36.6GW of electricity at 1:30pm.

The Queen’s Speech? Strictly Come Dancing or Call the Midwife? How does Christmas telly affect demand for electricity?

Like many of us, the forecasters in our control room will be looking closely at the TV schedules for Christmas Day – not necessarily to see what to watch, but assessing which programmes will get the highest viewing figures and therefore cause the highest TV pickup. TV pickups are the increase in demand for electricity at the end of popular TV programmes, when we collectively get off our sofas and boil the kettle or open the fridge.

Last Christmas, the biggest pickup was BBC One’s Call the Midwife with 380 megawatts; the equivalent of 190,000 kettles boiling at the same time. The largest ever Christmas Day pickup was in 1996, after an episode of Only Fools and Horses, measuring 1,340 megawatts. The same amount of electricity could have baked 30 million mince pies.

Thanks to on demand and catch-up TV, pickups are less common – but we’ll still be watching closely on Christmas Day.