Clean Energy | March 27, 2023

Mixergy raises £9.2 million to convert hot water tanks into energy storage systems

Jessica Pothering
ImpactAlpha Editor

Jessica Pothering

ImpactAlpha, March 27 – Individuals wanting to lower their carbon footprints – and energy bills – are adopting solar panels, electric vehicles, heat pumps and induction stoves. Oxford-based Mixergy wants to add hot water systems to the list.

Hot water tanks “are a pragmatic, low-cost solution for energy storage—one that already has an established supply chain,” Mixergy’s Pete Armstrong told ImpactAlpha. “They’re a resource that’s not really being used. There’s an opportunity to unlock a lot of energy storage by redesigning the product.”

Mixergy’s smart tanks heat only the water that is needed, using technology developed by Armstrong and co-founder Ren Kang at Oxford University. The smart hot-water tanks can switch between oil and gas boilers as well as electric inputs, solar panels and heat pumps.

“If there’s a surplus of wind or solar anywhere in the grid, it can switch off the gas boiler and go electric,” Armstrong said.

The tanks effectively operate as energy storage systems for the home.

“They’re 10-times cheaper than batteries and last way longer,” about 25 years, Armstrong said, adding that hot water tanks also require fewer materials to produce than battery storage systems.

They can’t, however, store surplus energy to flow back into the grid.

“It’s simply a demand response” that helps homeowners and renters cut natural gas use by up to 20% and costs by as much as 40%, Armstrong said.

U.K. consumers faced the highest gas prices in Europe due to the war in Ukraine,

Early-stage funding

Mixergy raised £9.2 million ($11.3 million) to finance R&D for its smart water tanks and other products, like a combined smart tank-heat pump. The round was backed by the venture arm of Portuguese utility EDP and U.K. social innovation nonprofit Nesta.

Mixergy sells its tanks in the U.K. and Portugal via a network of independent installers. It’s also partnering with social housing owners and developers, who are incentivized through government funding initiatives to do energy upgrades. There are more than four million registered social, or low-income, housing units in the U.K. In Birmingham, Mixergy is helping retrofit 300 properties as part of the city’s goal to make its housing stock carbon neutral by 2030.

The company is also getting a boost from a U.K. government policy that bans gas boilers in new properties, starting in 2025.