How to choose commercial battery storage installers: a 2026 checklist
Nine checks to make before you hire commercial battery storage installers, with where to verify each one. This guide comes from an independent information site that does not install batteries.
A commercial battery installer does more than fit equipment. They size the system, design the fire safety, take the grid application through your network operator and, often, maintain the system for a decade or more. The checks below separate installers who can do all of that from those who mainly sell hardware. Most can be verified against a register or a document rather than taken on trust.
The checklist at a glance
- The design follows the current standards
- A track record of G99 connections
- Safety evidence for the exact product
- Manufacturer approval and warranty terms
- Assessed electrical competence
- MCS, only where it applies
- Insurance, in date and in the company's name
- Who takes the CDM 2015 duties
- The company behind the quote
1. The design follows the current standards
Ask: Ask for confirmation, in writing, that the installation is designed to BS 7671 as amended by A4:2026 (including the new Chapter 57 for battery installations) and to the IET Code of Practice for Electrical Energy Storage Systems.
Why it matters: Amendment 4 was published on 15 April 2026 and the previous edition of BS 7671 is withdrawn on 15 October 2026. An installer who cannot name the documents their design follows is not ready to design your system.
2. A track record of G99 connections
Ask: Ask which G99 applications they have taken through your network operator in the last two years, how long each took, and who will submit yours and when.
Why it matters: For most commercial batteries the connection, not the hardware, sets the programme. An installer who plans to apply after design sign-off is adding months.
3. Safety evidence for the exact product
Ask: Ask for conformity evidence for BS EN IEC 62933-5-2 (the system) and IEC 62619 (the cells and battery modules) for the model being quoted, not the manufacturer's range in general.
Why it matters: Your insurer and, on larger sites, the fire and rescue service will ask the same question. It is easier to get the answer before the order.
4. Manufacturer approval and warranty terms
Ask: Ask the manufacturer, not only the installer, whether the installer is approved for the product, and whether the warranty depends on that. Then read the warranty itself: its length, any energy-throughput or cycle limit, the capacity it guarantees at the end, and who honours it if the installer stops trading.
Why it matters: Battery warranties differ more than the headline "10 years" suggests, and some depend on who installed the system.
5. Assessed electrical competence
Ask: Check whether the firm is registered with an electrical certification scheme; registrations with the main schemes can be searched on the Electrical Competent Person register. Ask as well for two or three comparable commercial or industrial installations you can discuss with the client.
Why it matters: That register is aimed at householders and landlords: it shows the firm's electrical work is assessed, but not that it has delivered commercial battery projects. References close the gap.
6. MCS, only where it applies
Ask: For a small system, check the MCS certificate covers battery storage. For most commercial systems, do not treat MCS as the test.
Why it matters: MCS's battery installation standard (MIS 3012) covers installations up to 50 kW. Most commercial batteries are larger, so the checks above matter more.
7. Insurance, in date and in the company's name
Ask: Ask for certificates for employers' liability, public liability and, if they design the system, professional indemnity. Check the named company matches the one on the quote.
Why it matters: Employers' liability insurance is a legal requirement for employers and must cover at least £5 million, from an authorised insurer. The other two are not compulsory, but a commercial installer without them is carrying risk that could land with you.
8. Who takes the CDM 2015 duties
Ask: Ask who will act as principal designer and principal contractor, and what they need from you as client.
Why it matters: Under CDM 2015, client duties apply in full to a business carrying out a construction project. Where more than one contractor is involved, which is common once civils, cranage and grid works are counted, the client appoints a principal contractor to control the construction phase.
9. The company behind the quote
Ask: Search the company on Companies House: its status, how long it has traded, whether its accounts are filed on time, and who the directors are.
Why it matters: A battery warranty and maintenance contract can run for a decade or more. It matters whether the company is likely to be there to honour it.
Red flags
- A price before any data. A firm quote without your half-hourly meter data is a guess about size, and size drives most of the cost.
- No mention of the grid connection. A proposal that does not say who submits the G99 application, and when, has left out the longest part of the programme.
- No answer on planning. For an outdoor container, ask who prepares the planning application and who talks to the fire service; see battery storage planning permission.
- PAS 63100 as the commercial fire standard. It covers dwellings; see PAS 63100 explained.
- Guaranteed savings figures. Savings depend on your tariff, load profile and how the battery is operated. A credible proposal shows its assumptions instead of promising a number.
- Pressure to sign quickly. An expiring discount is not a reason to skip the checks on this page.
- Accreditations you cannot find. If a logo on a website does not match an entry on the issuing body's register, ask why.
How to compare quotes
Ask every installer to itemise their proposal the same way. A like-for-like comparison needs, at least:
| Line | What to check |
|---|---|
| Battery and power conversion | Usable capacity (kWh) and power (kW), chemistry, the inverter or power conversion system, and the product standards evidence |
| Controls and metering | The energy management system, what it optimises for, and any monitoring subscription after year one |
| Civils and installation | Base or plinth, cranage, cabling routes, and any indoor room works such as compartmentation and ventilation |
| Grid connection | The G99 application, network operator fees, and whether any reinforcement cost is included or excluded |
| Fire and safety | Detection, any suppression, separation or venting, and the design documents your insurer will need |
| Commissioning and handover | Testing, certification, operating manuals and training for your site team: what a full commissioning handover includes |
| Warranty and maintenance | Warranty terms (years, throughput, end-of-warranty capacity) and the cost and scope of the maintenance contract |
Just as important is what each quote excludes. Two proposals at the same price can differ by the cost of the grid works. For typical price ranges, see the cost guide; for the tax position, see capital allowances.
How this site handles quote requests
This site is published by SEO Dons Ltd. It is an information site, not an installer, and it holds no installer accreditations. If you request quotes through a form here, your enquiry is passed to installers who cover your area, and they contact you directly. The publisher may receive a fee for the introduction, and some installers may be clients of SEO Dons Ltd for marketing services; the privacy notice explains the details. None of that is a recommendation: apply every check on this page to any installer, however you found them.