How to compare three home battery installer quotes like for like
- Give all installers the same information so the quotes answer the same question.
- Compare usable capacity in kWh and continuous power in kW, not headline figures.
- Read the warranty for years, retained capacity, a cycle or throughput limit and labour.
- Check what is included: network notification, scaffolding, commissioning and backup wiring.
- Be careful with savings claims; ask for the assumptions behind them in writing.
Three installer quotes only help if you can compare them line by line. Give every installer the same brief, then check the same handful of numbers and inclusions in each quote.
Start with the same brief
Both the Energy Saving Trust and the Renewable Energy Consumer Code advise getting at least three quotes, from installers who are certified for the work. If each installer starts from different information, you will not be comparing like with like.
Give each one your last 12 months of electricity use, whether you have solar, and any plans for an electric car or heat pump. The Renewable Energy Hub suggests asking for a design based on your own usage. Say clearly whether you want power-cut backup, because it changes the equipment. Our battery size guide helps you set a sensible starting point.
Line up the numbers that matter
Copy these into one table, one column per installer.
- Usable capacity in kWh. The Renewable Energy Consumer Code guidance for sellers says quotes should give usable capacity, not nominal, because batteries are not fully discharged. E.ON Next gives the example of a 10 kWh battery with 90% depth of discharge, which offers 9 kWh usable.
- Continuous power in kW. This sets how much the battery can run at once. The inverter can also limit output, and the lower figure applies.
- Round-trip efficiency. The share of energy you get back out. E.ON Next says modern residential batteries typically reach 85% to 95%. Ask the installer to state the loss.
- Warranty. Years, retained capacity at the end, any throughput or cycle limit, and whether labour is covered. Warranty terms differ more than headline years suggest.
- Backup. Whether the system works in a power cut, what it can run and for how long.
Our compare-for-yourself tool lets you check published specifications for products an installer proposes.
Use one table
Put the three quotes side by side with the same rows. A missing figure is as useful as a bad one: it tells you what to ask.
Check what is included
Two quotes with the same battery can differ by what surrounds it. Ask whether each price includes scaffolding, electrical work, the network operator application and VAT, and who handles that application from start to finish, a point the Renewable Energy Hub raises.
The installer normally notifies your network operator, as MCS explains. Ask to see the commissioning paperwork you will receive. The consumer code guidance also says a written quote should state the location, weight and dimensions, safety instructions, expected lifetime, replacement cost and maintenance needs. If a quote omits several of these, ask for them before you decide.
Treat savings claims with care
The same guidance says savings estimates must be realistic and should use your own circumstances, not standard assumptions, and that an inaccurate estimate that influences your decision may be treated as binding. We are not going to give you a payback figure here, and you should be wary of any quote that offers one without showing the working. Use our home battery calculator as a cross-check.
Before signing, get the standard terms and a written performance estimate for your property. The consumer code says to keep upfront payments low, never over 25% of the contract price, and to check they are protected. It also says you have 14 days to cancel in most cases and not to sign away that right. Read the exact wording in your contract, as we have not reviewed every case.
Common questions
How many quotes should I get?
At least three, according to both the Energy Saving Trust and the Renewable Energy Consumer Code. Fewer makes it hard to see what is unusual.
Should I pick the cheapest quote?
Not automatically. Check that the same capacity, power, warranty, inclusions and backup are covered first. A cheaper quote may leave things out.
What deposit is reasonable?
The Renewable Energy Consumer Code advises never paying more than 25% of the contract price up front and checking that the money is protected.
Can I rely on the installer's savings estimate?
Treat it as a starting point. Ask for the assumptions in writing and check them against your own bills and a neutral calculator.
Related guides
Want to know which battery size fits your home?
Use our free calculator to get a size, savings and payback estimate.