£1.4bn
spent in 2025 switching wind farms off and gas plants on
Britain’s Hidden Battery
Britain has a hidden battery. Big enough to change how we store energy for good. It’s sitting in millions of homes and buildings. Here’s how we switch it on.
Last year Britain paid £1.4 billion to throw clean energy away
When the wind blows harder than the grid can handle, wind farms are paid to switch off and gas plants are paid to switch on. Households and businesses pay for both, for electricity that was never used.
The wind we wasted could have powered every home in Lon for a year.
10 TWh
of GB wind curtailed in 2025
2.5m
homes in London it could have powered for a year
Most buildings already have a way to store that energy
Millions of hot water cylinders sit in homes, offices and even our most iconic landmarks. Every one of them could storeenergy as heat. Connected, they add up to the biggest battery Britain has never used.
10m
hot water cylinders already installed across UK homes
70 GWh
of storage, if every one were connected
1m
electric cars’ worth of battery, sitting in our homes today
Mixergy turns the cylinder into a thermal battery
British-made technology that stores energy as heat and releases it exactly when it’s needed. It learns your routine and heats only the water you’ll use. It charges when power is cheap and green, and holds off at peak when the grid asks.
Works with a gas or oil boiler, a heat pump, solar PV or direct electric. Designed and manufactured in the UK.
40%
less energy on hot water than a conventional cylinder
Heats only
what the home or building needs
Flexes
with the grid, charging when power is cheap, holding off at peak times
Lower bills. And now it pays you back.
Heating only what you use cuts the cost of hot water. Letting your cylinder help the grid earns you a share of the payments. Both, from the tank you already own.
Mixergy Flex Rewards is the UK’s first hot water flexibility rewards programme Your cylinder holds off at peak, the grid pays, and you get a share.
£100 to £180
a year off hot water, per home.
Based on combined real-world data from Mixergy homes, from North Devon to Birmingham.
Up to £250
a year with Mixergy Flex Rewards, where eligible.
Thousands of tanks together are sold as flexibility, in the same markets as big batteries. Your share builds up in your Flex Rewards balance.
Already Switched On
Savings of up to 40% are compared with a conventional cylinder, and the typical £100 to £180 a year per home comes from combined real-world Mixergy case study data, with actual savings depending on being connected, heat source, hot water use and tariff.
Flex Rewards earnings of up to £250 a year are the top of the modelled range, not a typical figure, and depend on eligibility, region and your tank’s set-up. Full T&Cs.
The 70 GWh storage figure, the national comparisons drawn from it and the £1.5 billion a year off bills are Mixergy analysis based on published industry data and show what ten million connected cylinders could do rather than a forecast, while the wind curtailment figures and the London comparison are from Montel, Curtailed Renewables in GB and Ireland in 2025 (January 2026).
