Battery storage for heat pump homes

A heat pump runs on electricity, and electricity costs very different amounts at different times of day. On an off-peak tariff the overnight rate is a fraction of the daytime rate. A home battery charges at the cheap rate and runs the heat pump, and the rest of the house, through the expensive hours. That is the whole idea. It works whether or not you have solar panels, and it is why we now fit batteries alongside heat pumps in Guildford and across Surrey.

What it does to the bills

A chapel conversion near Guildford that we look after, built in 1862 with a 6 kW heat loss, runs on an 18 kWh sodium-ion battery and Octopus Intelligent Go. The overnight rate is 3.5p per kWh against a daytime cap rate of 26.32p. In heating season the battery carries the house through the day down to about 6°C outside; below that it tops up at the day rate. Over a year most of the heat pump's electricity is bought at the overnight price rather than the daytime one.

Rule of thumb from that experience: about 3 kWh of battery for every 1 kW of heat loss if you want to cover a full winter day. A heat loss survey gives you the figure.

Battery installations to an existing home are zero rated for VAT. The prices below are what you pay.

Two options

Eleven Energy sodium-ion. Sodium, not lithium. Abundant, cold-proof, no cobalt.

Made in the UK by a Cambridge company. Sodium cells instead of lithium, so no cobalt and no lithium brine mining. Rated from minus 20°C to 55°C, so it can go in a garage or outbuilding without heating. 10 year and 8,000 cycle warranty on battery and inverter. Works with Octopus smart tariffs. Indicative installed prices: 9 kWh £5,800. 18 kWh £7,600. 36 kWh £12,600.

Fogstar lithium. The budget option.

Fogstar battery and inverter bundles, LiFePO4 chemistry, well proven and widely used. Sizes from 10 kWh to 64 kWh. 10 year warranty. Indicative installed prices: 10 kWh £3,900. 32 kWh £6,200.

Both are sized to the house, both are installed and commissioned by us, and both are set up on your tariff before we leave.

What we need to know

Your heat loss or your annual electricity use, your tariff, whether you have or plan solar, and where the battery can go. Send an enquiry and we will come back with a size and a price. Get a heat pump quote.

Last updated 20 September 2026.