Hot water and space heating systems designed around compact thermal storage cut energy consumption and social landlord running costs in 625 homes across Scotland.

Installing thermal batteries at scale, including alongside solar PV and heat pumps

Replacing electric heating and hot water cylinders, and reducing gas use, in 625 social housing homes

Lowering energy use as heat storage needs less gas and electricity to make hot water

The challenge

Over 25% of Scottish households were living in fuel poverty in 2016. People living in social housing more likely to be in fuel poverty than those in private housing.

Could social landlords help reduce residents’ fuel bills by implementing local solutions designed around thermal energy storage?

The solution

In response, the Scottish Government’s Local Energy Challenge Fund backed EastHeat in 2016. It was the largest residential heat storage project in Europe at the time and saw Sunamp thermal storage installed in 625 homes.

Over 700 heat batteries were fitted in homes with no gas connection to replace electric heating and hot water, and in other properties to reduce gas and electricity use by being installed alongside solar PV and heat pumps.

The project selected houses and apartments of many sizes located in rural, semi-rural and urban settings across Edinburgh, Lothian and Falkirk managed by Castle Rock Edinvar Housing Association (now called Places for People) and East Lothian Housing Association.

Solar panels on a house part of the EastHeat project

Residents with solar PV combined with Sunamp heat batteries had most of their hot water supplied by energy from their roof panels.

The benefits

The EastHeat trial interim report concludes that fuel poverty is being alleviated by using less energy to make hot water.

Surveys of residents at the time found that the majority saved money on their fuel bills.

In one- and two-bedroom properties with gas combi boilers and PV on the roof, solar consumption was much higher because of the heat batteries, with 55-63% of the hot water coming from solar PV. The Sunamp batteries dramatically reduced the amount of gas or electricity used to make hot water.

The old systems had poor water pressure. Residents liked that the Sunamp heat batteries gave them hot water at mains pressure on demand. Residents were also happy to have more cupboard space freed up by their bulky hot water cylinders being replaced with slimline heat batteries.

For the housing associations, costs were reduced because the batteries require no mandatory annual maintenance (unlike gas boilers and unvented cylinders) and no legionella testing is needed since each battery holds less than 5 litres of water. Additionally, the batteries’ compact size released storage space in each home, helping housing associations meet mandatory space standards.

A Sunamp thermal battery inside a small cupboard below a gas boiler

A Sunamp heat battery fitting neatly below a combi gas boiler in a Castle Rock Edinvar home. (Stewart Attwood Photography).  

“It has definitely made a difference to us. We are already seeing a dip in our fuel costs, and hot water seems to come through much faster than it did before. The installation went smoothly and the heat battery fits into a small cupboard.”

Resident of a two-bedroom house in Lothian.

The technical details:

  • Storage capacity: 766 heat batteries (4.4MWh)
  • Heating source: solar PV, electricity, gas and heat pumps connected to Sunamp heat batteries

Additional Information

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