Should I Add a Battery With My Heat Pump?

What does a battery do with a heat pump?

A home battery stores electricity so it can be used later. Paired with a heat pump, it lets you run the heat pump on stored electricity during expensive peak periods instead of drawing from the grid. The battery is charged either from the grid during cheap off-peak hours, from solar PV panels during the day, or a combination of both.

For example, on a time-of-use tariff like Octopus Cosy, electricity is cheaper during off-peak periods. A battery charged during those periods can power your heat pump in the evening when tariffs are higher. This reduces your effective electricity cost and therefore your heating cost.

How much does a battery cost?

A typical home battery system costs £3,000–£6,000 installed, depending on capacity (usually 5–15 kWh) and whether it is AC-coupled or DC-coupled with solar. Larger batteries cost more but can store more cheap electricity. The battery is installed alongside the heat pump, typically in a utility room, garage or cupboard.

It is important to note that finance for the heat pump does not cover battery storage. If you want both, the battery would need to be paid for separately or through a different arrangement. We discuss all costs clearly during your quote.

How much can a battery save on running costs?

With a time-of-use tariff, a battery can reduce your heat pump running costs by 20–30% by shifting electricity consumption to cheaper periods. The exact saving depends on the difference between your peak and off-peak rates, the battery capacity, and your daily heating demand.

With solar PV, the savings can be higher. Solar generates electricity during the day, the battery stores any surplus, and the heat pump uses that stored energy in the evening and overnight. In summer, a well-sized solar and battery system can run the heat pump for hot water almost entirely on stored solar. In winter, solar generation is lower, so grid charging becomes more important.

Is a battery worth it without solar panels?

Yes, if you are on a time-of-use tariff. The battery charges during off-peak hours and discharges during peak hours, reducing the effective electricity price you pay for heating. Without a time-of-use tariff, the savings are minimal because you pay the same rate regardless of when you use electricity.

If you are on a standard flat-rate tariff, a battery alone provides little benefit. In that case, it makes more sense to either switch to a time-of-use tariff first, or add solar PV so the battery has a free source of electricity to store.

Does a battery provide backup power during a power cut?

Most standard home battery systems do not automatically provide backup power during a grid outage. They are designed to reduce running costs, not to act as an uninterruptible power supply. Some systems can be configured with a backup outlet or automatic transfer switch, but this adds cost and must be specified during installation.

If backup power is important to you — for example in a rural area with unreliable grid supply — let us know during your quote and we can discuss options. A dedicated backup battery or generator may be more appropriate depending on your needs.

What size battery do I need for a heat pump?

The right battery size depends on your daily heating demand, your tariff structure, and whether you have solar. As a general guide, a 10 kWh battery can store enough electricity to run a typical heat pump for 3–4 hours at peak output, or longer at lower loads. For most Scottish homes, a 10–15 kWh battery paired with a time-of-use tariff is a practical choice.

A heat-loss survey determines your heat demand, and from there we can advise on the battery capacity that would give the best return. Oversizing the battery increases cost without proportional savings, so getting the sizing right matters.