Air Source Heat Pump with Heat Battery in London

The Challenge

The property had originally been two separate flats, each with its own heating system:

• Ground floor: Heated by a gas combi boiler with standard convector radiators.

• Basement level: Heated and supplied with hot water by a 9 kW Heatrae Sadia Electromax, essentially an electric boiler setup with a thermal store.

Because of the high running costs of the electric boiler, the basement bathroom had been mothballed and was mainly used for storage. The family relied only on the ground-floor bathroom, powered by the combi boiler, which was causing some issues in the mornings.

Our mission was clear: restore the basement bathroom to full use, reduce energy costs, and improve comfort across the property.

Our Solution

After reviewing the options, we replaced the electric boiler with a Sunamp Thermino ePlus 150 heat battery.

This approach avoided the extensive and costly pipework that would have been required to connect a hot water cylinder to the heat pump. Running pipes through the son’s bedrooms would have meant major disruption, boxing-in, and redecorating, all of which we wanted to avoid.

By using the heat battery, we were able to:

• Take hot water duties away from the heat pump (reducing strain and improving efficiency).

• Charge the battery at night using off-peak electricity at just 7p/kWh.

At that rate, the Thermino takes 2.5 hours to charge the equivalent of a 3 kW heating element. For a family of three, that provides a full day’s hot water for just 52p. Over a year, that works out at only £189.80, a huge saving compared to the old setup.

The Heat Pump

We installed a Grant Aerona³ 10 kW air source heat pump to handle the heating load only, which now connects to ground and basement radiators.

The new heat pump uses 5,268 kWh of electricity per year but delivers 18,229 kWh of heat energy in return!

This is an average efficiency across the year of 346 %.

This excellent performance was possible thanks to the customer’s willingness to upgrade radiators where needed, which allowed us to keep the heat pump’s flow temperature capped at 50 °C a key factor in making heat pumps work effectively in older homes.