A UK solar battery stores electricity for later use. It can move midday solar into the evening, charge from the grid during cheaper tariff periods, and provide backup when the system includes dedicated backup hardware. It does not automatically make every solar installation more profitable.
Choose storage from measured household demand and a clear operating goal, not capacity alone.
What a home battery can do
Solar self-consumption is the share of generated electricity used at home rather than exported. A battery can increase it by charging when production exceeds demand and discharging later.
On time-of-use tariffs, storage may also charge from the grid at a lower price and discharge during expensive periods. Some systems can export during high-value Smart Export Guarantee windows or participate in flexibility services.
Each use needs compatible controls, tariff permission, metering, and an economic model that includes energy loss.
Capacity and usable capacity
Battery capacity is stated in kilowatt-hours. Nominal capacity describes total stored energy; usable capacity is the portion available under the manufacturer's control limits.
Use half-hourly consumption and solar data to estimate the energy regularly available to shift. A large battery that often remains empty or full adds cost without adding proportional benefit.
Energy Saving Trust describes 5 kWh as a common reference size and reports around 9 kWh for homes with higher electrical demand such as heat pumps. Those are context points, not universal recommendations.
Power matters as much as energy
Power, measured in kW, controls how quickly a battery can charge or supply the home. A 10 kWh unit with a 3 kW output cannot fully support simultaneous high-power cooking, showering, heating, or EV charging.
Check continuous and peak power, inverter limits, single- or three-phase design, and which circuits are supported during backup. Capacity tells you how long energy may last; power tells you what can run at once.
Backup is a separate design
Many grid-connected batteries stop supplying the home during a power cut unless an approved backup gateway, isolation arrangement, and protected circuit are installed. This prevents unsafe energisation of the network.
Ask whether the proposal provides whole-home backup, selected circuits, or no backup. Confirm transition time, maximum power, solar operation during an outage, earthing, battery reserve, and manual recovery.
Do not infer backup capability from the presence of a battery.
Battery cost and return
Energy Saving Trust reported a broad installed range of £1,500 to £10,000 and about £4,600 for a 5 kWh battery system. Equipment, chemistry, power, backup hardware, installation timing, controls, location, and electrical work explain much of the variation.
Estimate annual value from avoided peak imports, additional solar self-use, eligible exports, and flexibility payments. Subtract charging cost, round-trip losses, finance, degradation, and expected replacement.
Compare solar-only and solar-plus-battery options in the UK cost and payback guide.
Round-trip efficiency and degradation
Some electricity is lost while charging, storing, and discharging. If a battery receives 10 kWh, it will return less than 10 kWh to the home.
Capacity also declines with calendar age and cycling. Compare warranted years, cycle limits, retained capacity, throughput, operating temperature, permitted use, and claim process. A long headline warranty can contain conditions that materially limit coverage.
Use an efficiency assumption in every tariff-arbitrage calculation.
AC-coupled and hybrid systems
A hybrid inverter can coordinate panels and a compatible battery through one architecture, often making sense for a new installation. An AC-coupled battery has its own power-conversion equipment and can be easier to add to existing solar.
The better choice depends on compatibility, conversion pathways, backup, existing warranties, monitoring, DNO requirements, and expansion plans. Ask the installer to draw the energy flows and state the conversion limits.
Avoid locking into proprietary equipment without understanding replacement and expansion options.
DNO connection requirements
Battery inverters are generation equipment from the network's perspective because they can export. Adding a battery can change aggregate inverter capacity and the applicable G98 or G99 process, even where export is limited.
The installer should identify every inverter, type-tested device, export limitation scheme, and connection pathway. Keep DNO approval or notification records.
Read DNO applications for solar panels before assuming an existing solar approval covers new storage.
SEG and grid charging
SEG suppliers set conditions for storage exports. Some may accept exports that include grid-charged electricity; others may require evidence, declarations, specific equipment, or controls.
A high evening export rate can be attractive, but test the complete cycle: import charge rate, losses, export rate, battery wear, standing charge, and tariff eligibility.
Compare SEG tariffs using actual export windows rather than the maximum advertised rate.
Installation and safety
Battery location affects temperature, access, fire separation, weather exposure, cable routes, ventilation, impact risk, and maintenance. The installer should follow product instructions, electrical standards, building requirements, and the applicable MCS battery standard.
Ask for isolator locations, emergency instructions, labels, commissioning records, firmware and monitoring ownership, and a single-line diagram. Inform the home insurer and follow any notification requirement.
VAT treatment
Electrical storage batteries became qualifying energy-saving materials in specified Great Britain residential and charitable installations from 1 February 2024. Standalone batteries, retrofits, and batteries installed with qualifying generation can fall within the temporary zero-rate rules when conditions are met.
The temporary GB zero rate is scheduled through 31 March 2027. Northern Ireland differs. The installer is responsible for charging the correct VAT, so read the UK solar VAT guide.
Battery quote checklist
- Nominal and usable kWh.
- Continuous and peak kW.
- Chemistry, enclosure, and location limits.
- Round-trip efficiency assumption.
- Solar, grid, and export control modes.
- Backup scope and protected circuits.
- DNO process and export limitation.
- Warranty years, cycles, throughput, and retained capacity.
- Monitoring access and software dependency.
- Installed cash price, VAT, and expected replacement.
A UK solar battery is strongest when it solves a measured timing problem. Size it around repeatable daily energy flows, then test the result against conservative tariffs and warranty conditions.