Put every quote on the same basis before comparing prices: the battery's usable capacity, the inverter and its rating, whether backup is included, where the battery will go, how it will be connected to the network, and all three warranties. Then divide the price by the usable kWh and compare it with the official median for that size in 2025/26: £1,300 per kWh under 6 kWh, £890 for 6 to 11 kWh and £630 for 11 kWh or more. Finally, check which tariff the savings figure assumes, and whether you can join it.
Guide · Published by SEO Dons Ltd · Updated 28 September 2026
Step 1: put the quotes on one page
Quotes arrive in different formats, and the one that looks cheapest often leaves something out. Copy each into the same grid before you compare anything:
| Line | Quote A | Quote B | Quote C |
|---|---|---|---|
| Battery make and model | |||
| Usable capacity (kWh) | |||
| Inverter: make, kW, hybrid or AC-coupled | |||
| Existing solar inverter kept or replaced | |||
| Backup: none, one socket, circuits or whole home | |||
| Proposed location and fire-safety work | |||
| Network route: G98 notification or G99 application | |||
| Battery warranty: years, % retained, throughput cap | |||
| Inverter warranty (years) | |||
| Installer workmanship guarantee (years, insured?) | |||
| Total price, VAT shown | |||
| Deposit and payment stages | |||
| Tariff and usage behind the savings figure |
A blank cell is a question to send back to the installer, not a line to guess.
Step 2: price per usable kWh
Capacity is quoted two ways. Nominal capacity is what the cells hold; usable capacity is what the battery lets you draw after keeping a reserve. Fox ESS’s EVO 10 holds 10.24 kWh with a 95% depth of discharge, so about 9.7 kWh is usable. E.ON Next lists its standalone battery as 5.12 kWh with 4.6 kWh usable. Tesla quotes the Powerwall 3’s 13.5 kWh and Enphase the IQ Battery 5P’s 5.0 kWh as usable figures. Divide each quote’s price by its usable capacity. E.ON Next, for example, states its Sunsynk Elite as 5.12 kWh with 4.6 kWh usable, worked through per kWh in the E.ON Next battery guide.
Then set that figure against the official median for the size, from DESNZ’s statistics on MCS-certified installations in 2025/26. This site treats anything within 20% of the median as typical; that is a rule of thumb, not a valuation.
| Battery size | Median per kWh | Typical range (±20%) | Median for a common size |
|---|---|---|---|
| Under 6 kWh | £1,300 | £1,040 to £1,560 | about £6,500 for 5 kWh |
| 6 to 11 kWh | £890 | £712 to £1,068 | about £8,900 for 10 kWh |
| 11 kWh or more | £630 | £504 to £756 | about £8,500 for 13.5 kWh |
Illustrative example. A quote of £7,500 for a battery with 10 kWh usable is £750 per kWh. That sits inside the typical range for the 6 to 11 kWh band (£712 to £1,068), a little below the median. The same £7,500 for a battery with 7 kWh usable would be about £1,071 per kWh, just above the range, and worth a question.
A price well below the range is not automatically a bargain or a warning. Large energy suppliers publish packages below the medians: Octopus’s battery-only installation of about 10 kWh, from £5,336, is roughly £521 per kWh of rated capacity, and our page on 10 kWh home batteries compares five products sold at that size. What matters is that a low price includes the same things as a higher one. The quote checker runs this comparison for you.
For a quote that bundles panels and a battery, divide the price by the system’s kWp and the battery’s usable kWh separately and hold each against the official figures in the solar panels and battery cost guide. The cost per kWh delivered post explains why a price per kWh of capacity is only half of the picture.
Step 3: check what each price includes
These are the lines where quotes differ most, and where a cheap quote tends to save its money:
- The inverter. A hybrid inverter replacing your solar inverter, a separate battery inverter alongside it, or one built into the battery: each changes the price, the efficiency and what happens to your existing system. See AC vs DC coupled batteries.
- Backup. Anything from nothing, to a single emergency socket, to selected circuits, to a whole-home gateway. Tesla’s list prices show the Backup Gateway 2 alone adds £975. See home battery backup.
- Location and fire safety. PAS 63100, the specification for batteries in homes, rules out bedrooms, escape routes and lofts and sets fire-separation rules for indoor rooms. A compliant spot may need longer cable runs, fire-rated boarding, an alarm or an outdoor location. Ask where the battery will go and why it complies. See PAS 63100 explained.
- Electrical work. Some homes need a new consumer unit, isolators or an upgraded supply before a battery can be connected. A quote that excludes “any remedial work” can grow after the survey.
- Network approval. If the combined rating of every inverter exceeds 16 A per phase (about 3.68 kW on a single-phase home), the installer must make a network application under G99 before connecting, which takes time and can come with an export limit. Ask which route applies and who handles it.
- Commissioning and registration. Some warranties depend on the installer registering the battery: Enphase’s lapses if the battery is not registered within 45 days of activation, and Tesla’s full term needs the Powerwall kept online.
- VAT. Installed batteries in homes are zero-rated until 31 March 2027 under HMRC’s VAT Notice 708/6. A quote should not add VAT to the battery or its installation.
Step 4: compare the three warranties
Every battery installation carries three separate promises, and quotes often mention only the first:
- The battery warranty from the manufacturer: years, the percentage of capacity promised at the end, and any throughput cap. Tesla promises 80% at 10 years; Fox ESS 70% at 10 or 12 years up to a throughput cap; Enphase 60% at 15 years or 6,000 cycles.
- The inverter warranty, which may be separate. Fox ESS’s battery policy excludes inverters, including the one inside an all-in-one unit.
- The installer’s workmanship guarantee. Members of the RECC consumer code must give at least two years, transferable on a house sale and insured if the business stops trading.
Then ask who you would claim through. Most manufacturers route claims through the installer, which is why the GivEnergy administration left so many owners without a clear route. How long batteries last compares the main warranties.
A warranty is only as good as the company behind it. The 12-year promise on a GivEnergy battery now depends on a company in administration, which is why the claim route matters as much as the years.
Step 5: test the savings claim
A savings or payback figure is only as good as the assumptions behind it. Ask each installer for:
- The tariff it assumes, and whether you can join it. Octopus Flux needs solar panels; Intelligent Octopus Flux is currently limited to customers who bought solar and a battery from Octopus; overnight EV tariffs are aimed at homes with an electric car.
- Your annual use and how much of it falls in the evening.
- Round-trip losses and capacity fade. This site’s model assumes 90% round-trip efficiency and capacity averaging 90% of new over ten years.
As a reference point, this site’s model gives a 10 kWh battery with 4 kWp of solar a saving of about £379 to £455 a year on Octopus Flux, depending on region, against £141 to £181 on a flat tariff. At Octopus’s £5,336 that is a payback of roughly 12 to 14 years on Flux. A quote promising a payback of five or six years for a similar home is worth asking about. See is a home battery worth it?.
Step 6: payment terms and protection
Compare deposits, stage payments and finance terms as carefully as the price. Under the RECC consumer code a deposit should never exceed 25% of the estimated cost, and the deposit and any advance payment together must not exceed 60%. For finance, compare the APR and the total amount payable, not the monthly figure. Our guide to choosing a battery installer covers consumer codes, cancellation rights and the registers to check.
Red flags in a quote
- A battery described only by capacity, with no make or model.
- No mention of where the battery will go, or a proposed spot in a loft, hallway or bedroom cupboard.
- A savings figure with no tariff named, or a tariff you are not eligible for.
- “MCS approved battery”: MCS certifies installers and installations, not battery products.
- A price that expires the same day, or a large discount for signing at the first visit.
- VAT added to an installed battery, or no VAT line at all.
Putting it together
Once each quote is on the grid, the comparison is usually obvious: one leaves out backup, one assumes a tariff you cannot have, one prices a new inverter the others do not. Compare the complete ones on price per usable kWh and warranty. If you want quotes to compare, request battery storage quotes through this site, and run each one through the calculator with your own region and usage.
Questions people ask
How many home battery quotes should I get?
Two or three from different installers, ideally including one for a different battery brand. One quote gives you nothing to compare, and more than three rarely changes the picture once each is on the same basis.
What should a home battery quote include?
The battery make, model and usable capacity; the inverter's make, power rating and type; any backup equipment; the proposed location and any fire-safety work; the network notification or application; commissioning and warranty registration; the manufacturer's battery and inverter warranties and the installer's workmanship guarantee; the total price with VAT shown; and the payment terms.
Is price per kWh a fair way to compare battery quotes?
It is the best single number, as long as you divide by usable rather than nominal capacity and compare like with like. Small batteries always cost more per kWh because installation costs much the same whatever the size, which is why the official medians are split into three size bands.
Should a home battery quote include VAT?
It should show VAT at 0%. Installed batteries in homes are zero-rated until 31 March 2027 under HMRC's VAT Notice 708/6, including standalone batteries and batteries added to existing solar. From 1 April 2027 the rate becomes 5%.
What is a normal price for a home battery?
The official medians for MCS-certified batteries fitted in 2025/26 were £1,300 per kWh under 6 kWh, £890 per kWh for 6 to 11 kWh and £630 per kWh for 11 kWh or more: about £6,500 for 5 kWh, £8,900 for 10 kWh and £8,500 for 13.5 kWh. Large suppliers publish lower package prices, such as Octopus's £5,336 for about 10 kWh.