The useful starting point
Ask for a whole-system price with an exact specification. Price per kWh is useful only when you understand what has been included.
Define the system before the price
A “10 kWh battery price” can mean bare modules, modules with a controller, a complete inverter package, or a fully installed system. Those are different purchases. A useful proposal names the equipment and lists the work needed to make it operate at your property.
There is also a difference between adding storage to working solar and installing solar and storage together. Retrofitting can require different equipment and electrical work. Ask whether the existing inverter is retained, replaced or supplemented.
Use public figures as context
The Energy Saving Trust gives around £4,600 for a 5 kWh battery system in its public guidance. This is a broad reference, not a quote for your address. Larger capacities and different inverter or backup arrangements should not be priced by simply multiplying that figure.
For a specific product, our Powerwall 3 guide explains published installer examples and their scope. Advertised “from” prices still need checking against your survey and chosen configuration.
Make a comparison sheet
| Compare | Record this |
|---|---|
| Energy | Usable capacity at commissioning, reserve settings and module count |
| Power | Continuous charge/discharge limits and site restrictions |
| Equipment | Battery, controller, inverter, gateway and metering |
| Work | Cabling, protection, mounting, access and commissioning |
| Support | Parts, labour, call-outs, response route and warranty conditions |
| Payment | Full cash price, VAT treatment, deposits and finance total if used |
What price per kWh can and cannot tell you
If one hypothetical installation is £6,000 for 10 kWh usable, its installed cost is £600 per usable kWh. If another is £8,000 for 13.5 kWh, it is about £593 per usable kWh. Those figures are nearly equal, but the systems may have different power, support and backup capabilities.
More capacity can also produce less value per pound if the home cannot use it. Keep your realistic shiftable demand unchanged when comparing sizes. Ask the battery tool to show the effect before assuming a bigger unit is better value.
Be precise about backup and warranty
“Backup capable” can describe a feature the product supports, not work included in the price. Require a list of supported circuits and the equipment needed to isolate safely from the grid. Ask how solar recharging works during an outage.
Read the warranty beyond its headline duration. Throughput, retained capacity, operating conditions and the person responsible for labour all matter. The cheapest total is not automatically the lowest ownership cost, but an expensive brand label is not evidence of better service either.
Published information supports your research. Your installer should confirm the exact product, suitability, scope and terms for your property.
Suggest a correction ↗Your next useful step
Put the information to work.
Take the questions that matter to your project, explore the numbers and decide what to ask next.
