The useful starting point
A search for a “10 kW battery” often means 10 kWh of storage. Confirm which figure you need: kWh is stored energy; kW is how quickly the system can deliver it.
Start with energy you can actually shift
A 10 kWh usable battery does not create a 10 kWh daily saving. It must have enough energy to charge, sufficient demand later, and a tariff difference or solar surplus that makes the cycle useful. A large battery that regularly sits full has money tied up in unused capacity.
Look at your smart-meter data across several seasons. Record grid use during expensive periods and, if you have solar, the surplus available after the home has used what it needs. Ask your installer to model winter as well as a bright summer day.
A worked capacity example
Suppose a battery has 10 kWh of usable capacity and you reserve 20% for backup. That leaves 8 kWh for routine use. If your evening demand is only 5 kWh, this scenario uses 5 kWh, not the full 8 kWh. At an illustrative 90% round-trip efficiency, delivering that energy takes about 5.56 kWh of charging electricity.
At fictional rates of 10p to charge and 27p of import avoided, the daily benefit is about 79p: £1.35 avoided less 56p charging cost. Multiply by realistic operating days, not automatically every day of the year. This example excludes standby use, degradation and maintenance.
What belongs in the price
| Line on the proposal | What to check |
|---|---|
| Battery modules | Exact model, usable capacity and number of modules |
| Power conversion | Included inverter or compatibility with an existing system |
| Installation | Cable routes, protection, location and commissioning |
| Backup | Gateway, circuit changes, supported loads and any exclusions |
| Aftercare | Warranty registration, labour, call-outs and support responsibility |
We do not have a verified national installed-price average for a 10 kWh system. Compare itemised local proposals with the same scope. Dividing total cost by usable capacity can be informative, but it does not price the value of backup or a stronger inverter.
Compare a larger fixed unit with a modular design
A product close to this capacity can be supplied as a fixed unit or assembled from modules. Tesla Powerwall 3 provides 13.5 kWh of usable energy; a SigenStor proposal depends on its controller and selected battery modules. Neither automatically becomes the better purchase because its capacity is closest to 10 kWh.
Use our Powerwall 3 versus SigenStor guide to compare the whole system, then run your own assumptions through the battery scenario tool.
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.
