What happens during a battery installation?
Short answer
A straightforward single battery is often fitted in about a day, with the power off for part of it. Gateways, earth rods, consumer unit changes, fire-separation works or moving solar strings add time. The bigger wait is often the DNO: G99 approval must come before installation.
Last checked 24 September 2026 · 4 sources
What should I know before deciding?
MIS 3012 requires risk assessment, CDM construction phase plan, commissioning procedure and handover.
Can I fit a battery and tell the DNO afterwards?
Only under G98 or G99 SGI-1. If total registered capacity on site, including existing solar, is 16 A per phase or less and the inverters are fully type-tested, install first and notify the DNO within 28 days of commissioning (G98 Form B with a cut-out photo). Several installs in one area within 28 days need prior approval.
SGI-1 (G99): units up to 32 A intrinsic but software-limited so aggregate <=16 A/phase - also install-then-notify (Form A3-3). Northern Ireland uses G98/NI and G99/NI.
What must be tested, recorded and handed over when commissioning a battery?
Commission to a documented procedure (MIS 3012 cl.4.1) using the App A checklist and BS 7671 certificate, verifying loop impedance and fault current in every mode. Hand over the PAS 63100 conformity statement, user instructions with alarm and battery-fire procedures, Part P and DNO records, the MCS certificate, and the export limit, generation limit and reserve settings.
Equipment tests: data/control, internet, displays/alarms, charge-discharge, thermal management, fire systems (App A Part 3). Export limitation tests per G100; backup switchover and RCD tests in island mode. Record inverter Registered Capacity as set (software limit) and the DNO-agreed export limit.
Does my battery installer need to be MCS certified?
It is not a legal requirement, but often matters. Octopus Flux asks for the MCS document, grant and loan schemes generally rely on certified installers, and MCS battery installers must follow MIS 3012 and the IET battery Code of Practice. Check the certificate covers batteries, not just solar.
MIS 3012 compliance mandatory for MCS:2025 contractors. Since 2024 MCS noted PAS 63100 applied indirectly via the IET CoP; BS 7671 A4 now requires it in dwellings.
What to do next
Ask the installer to show the proposed location, DNO route, backup arrangement and commissioning documents before work starts.
Sources
- MCS — mcscertified.com/wp-content/uploads/2025/02/MIS-3012-2025-V1.0.pdf
- dcode.org.uk — dcode.org.uk/assets/250307ena-erec-g98-issue-2-(2025
- BSI — knowledge.bsigroup.com/products/electrical-installations-protection-against-fir…
- Octopus Energy — octopus.energy/smart/flux/
Last checked: 24 September 2026