Home battery quote: 20 questions to ask before you sign
A battery quote is easiest to judge when the installer has answered the same questions as everyone else. Send these with your enquiry, or ask them before you agree anything.
Quick answer
Before signing a home battery quote, get the nominal and usable capacity, an itemised price, the exact location and how it meets PAS 63100, whether the network application is G98 or G99, the certificates you will receive, the warranty's years and energy limit, who honours it if the firm stops trading, and the invoice date for VAT.
The questions, in five groups
None of these is a trick question. A good installer will answer all of them in writing, and the answers make quotes from different firms comparable.
About the battery itself
- What is its nominal capacity, and what is its usable capacity? Please send the manufacturer's specification sheet.
- What is the inverter's power rating in kW, and is it a separate battery inverter or a hybrid unit?
- Does the price include backup in a power cut? Which circuits would it keep running?
- If I might want more storage later, can this model be extended, and what would that involve?
About the price
- Can you itemise the quote: battery, inverter, siting works, backup, protection devices, network application and certification as separate lines?
- What does the total come to per nominal kWh, and per usable kWh?
- What date will you invoice, and will any deposit be invoiced separately? (VAT on an installed battery goes from 0% to 5% on 1 April 2027.)
- Is anything in the quote not an energy-saving material, and charged at a different VAT rate?
About where it goes
- Where exactly will the battery go, and how does that location meet PAS 63100?
- What fire-resisting separation, ventilation or alarm work is needed there, and is it in the price?
- If it goes in the garage or beside the drive, how will it be protected against impact?
- Will I get a statement of conformity with PAS 63100 attached to the electrical certificate?
About the paperwork
- Will you notify the network operator under G98 or apply under G99, and who submits it?
- If it is G99, does the installation date allow for the operator's reply?
- Which edition of BS 7671, the Wiring Regulations, will the certificate be issued against?
- Will the battery be registered with MCS, and is battery storage listed on your MCS register entry?
About afterwards
- How long is the battery warranty in years, and what total energy or number of cycles does it cover?
- Who honours the warranty if your firm stops trading? Is any guarantee insurance-backed?
- Which consumer code does your firm belong to, and how are deposits protected?
- What does the handover include: shutdown instructions, what to do in a battery fire, monitoring set-up?
Why each group matters
The battery
Capacity on the label is nominal; what you can draw out is usable, and the two differ by model. DESNZ prices nominal capacity, so the official medians and your quote line up only if you divide by the same thing. The inverter's power rating decides the network route, and backup is an extra that two quotes may treat very differently. The price per kWh page works through nominal, usable and warranted kWh.
The price
An itemised quote is the single most useful thing you can ask for. The government's Warm Homes Loan Scheme rules list what a typical battery quote may include, from integration with an existing solar system to isolators and protection devices; if one quote names these and another doesn't, the totals don't compare. The invoice date matters because of the VAT step: see VAT on home batteries.
The location
PAS 63100, the specification for protecting homes against battery fires, rules out bedrooms, escape routes, lofts and cupboards opening into bedrooms, among other places, and sets out what an acceptable indoor spot needs. The work to meet it is often the most variable part of a quote; what adds to a battery quote covers each item.
The paperwork
MCS says storage over 3.68 kW needs a G99 application before installation; smaller systems are notified within 28 days. Amendment 4 to BS 7671, published on 15 April 2026, added a chapter on stationary batteries, and the previous edition was withdrawn six months later, so a certificate issued now should be against the amended edition. Battery storage is a separate MCS technology from solar panels: a firm certified for panels is not automatically certified for batteries. Check its entry on the MCS register. Our network application guide explains G98 and G99.
Afterwards
Which? says battery systems often come with a 10-year warranty, and warranties usually also limit the total energy covered. Ask who stands behind the warranty if the installer goes out of business, whether any guarantee is insurance-backed, and which consumer code the firm belongs to: codes such as RECC and HIES set rules on deposits and complaints. PAS 63100 also expects the user instructions to include how to shut the system down and what to do in a battery fire.
Answers that should make you pause
- A total with no breakdown, or a refusal to give usable capacity.
- A location in a loft, a bedroom or on a landing.
- A start date that leaves no time for a G99 reply.
- A "government grant" that pays for anyone's battery: there is no such national grant. See paying for a battery.
When the answers are in, set the battery line against the official median with the quote checker, or start again from the price calculator if the size has changed.
Sources (page last reviewed 3 November 2026)
- BSI / DESNZ: PAS 63100:2024, battery energy storage systems in dwellings (PDF), checked 3 November 2026.
- MCS: notifying distribution network operators (G98 and G99), checked 3 November 2026.
- MCS: find an installer (the public register), checked 3 November 2026.
- IET: Amendment 4 (2026) to BS 7671:2018 published 15 April 2026, checked 3 November 2026.
- DESNZ: Warm Homes Loan Scheme rules, version 3 (September 2026, PDF), sections 2.6 and 4.4 to 4.19, checked 3 November 2026.
- HMRC: VAT on energy-saving materials and heating equipment (Notice 708/6), sections 2.1, 2.3 and 2.19, checked 3 November 2026.
- Which?: solar panel battery storage (secondary source, page updated 30 October 2026), checked 3 November 2026.
- DESNZ: MCS certified domestic battery installation statistics (April 2024 to March 2026 workbook, published 28 May 2026), checked 3 November 2026.
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