Solar batteries and power-cut backup: what to ask

A battery can help you use solar electricity later in the day. Power-cut backup is a separate capability that needs to be specified in the system design.

What battery storage does

A compatible battery can store surplus solar generation for later use. Some systems can also charge from the grid using a suitable time-of-use tariff. The right arrangement depends on your equipment, tariff and pattern of electricity use.

Ask for a proposal that explains those assumptions. Storage has an upfront cost, and energy is lost during charging and discharging, so savings should be assessed for your circumstances.

Compare the tariff assumptions, not just the battery size

Ask to see the import and export rates used in the calculation, the amount of electricity expected to pass through the battery, and the allowance for charging losses. Compare the proposal with solar alone as well as with your current supply. A favourable cheap-rate window is useful only if the system can charge enough within it.

Suitable controls can help coordinate charging with changing prices, but compatibility and any ongoing fees should be confirmed before you commit. Request a realistic comparison for your usage; a headline saving from a different household is not a forecast for yours.

Do you need power-cut backup?

A standard grid-connected solar installation usually stops supplying power during an outage. Adding a battery does not, by itself, establish that your home will stay powered.

If backup matters to you, ask exactly what is included: which circuits or sockets are supplied, what equipment is required, whether switching is automatic, and whether solar can recharge the battery during an outage.

Capacity and output answer different questions

Usable capacity describes how much energy a battery can store. Power output describes how much it can supply at a time. Ask your installer to explain both against the equipment you want to run.

Capacity is normally stated in kilowatt hours (kWh), while charge and discharge power are stated in kilowatts (kW). Check the usable figure, not just the headline capacity. Also ask how much energy will be held back for backup, because that reserve changes the amount available for everyday use.

Questions for your proposal

• Is this for a new solar system or an existing installation?

• What usable capacity and power output are included?

• What does the warranty cover?

• What happens during a power cut?

• How will the system be monitored and supported?

Request a free survey from Solar Acre to discuss storage around your home, business or rural property.

Further reading: Energy Saving Trust: battery storage and solar power facts.

Content reviewed on 9 September 2026.