A partial solar eclipse, the deepest that the UK has seen in nearly 30 years, is happening on Wednesday evening.
The moon will swallow almost all of the sun, dimming the evening light slightly from about 6pm to just after 8pm.
The peak, when the moon will take its largest bite, will depend on where in the UK you are, but will be roughly between 7pm and 7.20pm.
If you’re not outside watching this celestial dance (wearing proper solar eclipse glasses, of course), try not to do your laundry.
This is the message that Octopus Energy, one of the UK’s largest energy providers, is telling customers.
‘When the moon blocks the sun on Wednesday, Britain will lose a chunk of its solar power just as millions of people are getting home and switching on their appliances,’ Kieron Stopforth, head of flexibility at Octopus Energy, tells Metro.
Octopus’ Eclipse Power Down initiative is offering free electricity the following weekend for using less power during the eclipse.
Why should we use less electricity during a solar eclipse?
Professor Chris Sansom, an expert in solar energy at the University of Derby, understands why Octopus has launched the scheme.
During the summer months, the UK sources a huge chunk of its energy from solar panels. It is pretty sunny, after all.
‘The dip in supply from solar during the eclipse could be significant, and the electricity supply companies are simply being cautious,’ Professor Sansom says.
‘They have a right to be slightly concerned because quite a significant proportion of our energy comes from solar.’
According to the Energy Dashboard at the time of writing, more than 35% of the energy surging through the power grid comes from the sun.
This figure will rise later today, Professor Sansom adds, as it gets sunnier.
On a sunny and bright day, solar farms can produce about 16 gigawatts (GW) of energy.
Turning to solar to keep makes sense given we’re most active while the sun is shining, including peak usage times at 5pm and 7pm.
Solar panels generate electricity even during cloudy or rainy days as UV rays – a special light humans can’t see – from the sun still cuts through.
But during a partial solar eclipse, all that is left of the sun are wispy streaks of fire from behind the moon, meaning little light will seep through.
The National Energy System Operator (Neso), which manages the electricity grid, expects solar production to fall up to 1.3GW, akin to losing the output of two nuclear reactors.
As the moon’s shadow races across the planet from north to south, solar plants in Wales, Devon and Cornwall will see the biggest decrease.
The solar eclipse in 2024 caused a massive decrease in solar generation in Texas, from 99.2% around noon to 7.6% by 1:45pm, according to the Electric Reliability Council of Texas.
The state was bathed in 16% less of its daily irradiance, or solar energy, at the peak of the eclipse, data scientists said.
We can’t simply turn to wind, another renewable energy source, either.
Professor Sansom says that the UK is being squeezed by a high-pressure system, encasing the country in heat, so there will be little wind to power turbines on Wednesday.
‘It is a double whammy,’ he adds.
Importing energy isn’t an option either, Professor Sansom says, as it’s too pricey and energy firms don’t want to foot the bill.
Gas plants will instead need to be fired up to compensate for this, Peter Connor, an associate professor sustainable energy policy at the University of Exeter, says.
‘Last Friday the demand at mid-day was just over 30GW and about 13.5 GW was from solar, by 6pm solar was about 2.6GW, by 7pm, or roughly the point when the eclipse is closest to the maximum, it was well 0.64GW so only about 2% of total supply at that point,’ says Professor Connor.
‘As the amount of power from solar went down the difference was picked up largely by natural gas burning power stations, which is often the case. The same thing will happen during the eclipse.’
Will energy bills need to go up because of the eclipse?
Energy companies have their reasons for encouraging customers to switch power-guzzling appliances off.
Powering up a gas plant can raise the price of a unit of electricity sold.
‘So if you are an energy company worried about the cost of the next increment – a price spike basically – then it may pay to encourage your consumers to switch off, and to provide an incentive to do so,’ Professor Connor says.
‘That could be lower prices for a fixed amount of time or some sort of points system which gives a discount on your bill, which is what Octopus offers.’
Both experts stressed that as scary as this might sound, don’t worry about the lights not turning back on after moon bids goodbye to the sun.
‘It’s very unlikely there is any danger of the UK running out of power,’ says Professor Peter.
Nor should you worry too much about whether you can keep the big light on during a total solar eclipse, when the sun is fully obscured.
The next total solar eclipse is not expected until September 23, 2090. A fair few decades away then.
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