With the number of solar and wind farms increasing all the time, our electricity grid is more complex than ever.
But sometimes more power is produced in one part of the country than can be used, so they are ordered - and paid - to shut down.
This is known as "constraint" and cost £1.2bn in 2021, which ultimately goes on to customers' bills. It is also a waste of low-carbon power.
That is why one grid operator and one power supplier are trialling the free electricity scheme. But is it fair?
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Balancing supply and demand on the electricity grid falls to operators including UK Power Networks. Its director of innovation, Ian Cameron, said the pilot Mr Bradley took part in aimed to see if customers could "soak up excess generation" rather than "turning down" renewable generators.
He said the grid needed consumers to "step forward and engage with the energy system".
The peak period for electricity demand is between 17:00 BST and about 21:00 BST, Mr Cameron added, and that drawing 15% to 20% away from that period "makes a significant difference".
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The "Power-Ups" are announced around a day before the free window. Customers living in certain postcodes and who have pre-registered, can take part.
Rosie Robison, a professor of social sustainability at Anglia Ruskin University, said it was important such schemes did not leave those on low incomes "doubly disadvantaged" because they could not make the most of them.
Those "with more resources" and "technical know-how" may find it easier to access the scheme and save money immediately, she said.
