The installation is usually a day: Tesla says a typical Powerwall installation takes a full day, with the power off for about four to six hours. The weeks before it depend on the network. A small system can be fitted first and notified to the network operator within 28 days of commissioning (30 days for SP Energy Networks). A larger one needs a G99 application before installation: SSEN aims to answer fast-track applications within ten working days, and UK Power Networks automatically approves applications where export stays under 5 kW.
Guide · Published by SEO Dons Ltd · Updated 6 October 2026
The stages at a glance
| Stage | What happens | What sets the timing |
|---|---|---|
| 1. Quotes | A survey, remote or in person, and a written, itemised price | How quickly installers can survey; get two or three for the same specification |
| 2. Accepting one | You sign, and usually pay a deposit | A 14-day cancellation period for contracts agreed at home, online or by phone |
| 3. The network | A G98 notification after installation, or a G99 application before it | G99 decisions take time; G98 needs no wait |
| 4. Installation day | The battery, inverter and any backup hardware are fitted and commissioned | Usually one day; the power is off for part of it |
| 5. Paperwork | Certificates, notifications and warranty registration | The installer’s admin, and deadlines such as warranty registration |
| 6. Tariff | Switching to a tariff that makes the battery pay | Supplier eligibility rules and, for export, an export meter number |
1. Quotes and the survey
A quote you can rely on follows a survey, because the battery’s location, cable route and consumer unit all affect the price. Some suppliers start remotely: Octopus, for example, asks you to complete a remote survey form and arranges a surveyor’s visit only if you cannot. If you have existing solar panels fitted by someone else, expect to be asked for their MCS certificate and the specification of the existing inverter, which the installer needs for the network paperwork.
This is the stage to compare. Ask for the same usable capacity, inverter power and backup in every quote so the prices line up, and check each one against the official median for its size before you sign.
The survey also settles where the battery goes, which moves the price. The installer should check the spot against PAS 63100, the fire-safety specification, and from 15 October 2026 the Wiring Regulations tell electricians to take account of it, as the BS 7671 Amendment 4 explainer sets out.
2. Accepting a quote: deposits and the 14 days
Once you accept, two sets of rules apply. Under the Consumer Contracts Regulations 2013, a contract agreed at your home, online or over the phone normally gives you 14 days to cancel. If you ask the installer to start inside that period, you can be charged for the work done before you cancel.
Deposits are capped by the consumer codes. RECC members may not take a deposit above 25% of the price, and deposit plus any advance payment may not exceed 60%; HIES protects deposits and stage payments up to 25% of the contract value or £5,000, whichever is lower. Some suppliers take less: Octopus asks for £500, which it describes as non-refundable once you sign its installation agreement.
3. The network operator: G98 or G99
This is the stage most likely to decide how long you wait. Every inverter that can export counts towards a limit of 16 A per phase, about 3.68 kW on a single-phase home.
- Under the limit (G98). The installer fits the battery and notifies the network operator afterwards: within 28 days of commissioning for National Grid Electricity Distribution, SSEN and UK Power Networks, and within 30 days for SP Energy Networks. Nothing waits on the operator.
- Over the limit (G99). The installer makes a G99 application before installation and cannot connect until the operator agrees. SSEN aims to respond to fast-track applications within ten working days. UK Power Networks automatically approves applications where the maximum export, after any export-limiting scheme, is under 5 kW. Others vary, and an approval can come with an export limit.
Adding a battery to existing solar is the commonest reason a small home crosses the limit, because both inverters count. A 3 kW solar inverter plus a 3 kW battery inverter makes 6 kW, which needs G99. A battery that replaces the solar inverter with one hybrid inverter may not.
The operator depends on where you live. For homes in Cardiff, Swansea and Newport it is National Grid Electricity Distribution, and for the north of Wales it is SP Energy Networks, as the battery storage Wales guide sets out.
4. Installation day
Tesla says a typical Powerwall installation takes a full day, with the power off for about four to six hours, or eight hours or more if extra electrical work is needed. Other systems are similar in scale: the battery and inverter are mounted, cables are run to the consumer unit, the system is commissioned and set up on its app. If backup hardware is included, it is wired at the same visit. Expect the installer to need access to the meter, the consumer unit and the battery’s location for the whole day.
5. Paperwork, and what to keep
By the end, or shortly after, you should have:
- An MCS certificate, if the installer is MCS certified for batteries under MIS 3012.
- An electrical installation certificate with a statement that the battery’s location meets PAS 63100, the fire-safety specification for batteries in homes.
- A Building Regulations notification, usually made by the installer through its competent person scheme.
- The network notification or approval from stage 3.
- The warranty registration. Some warranties depend on it: Enphase’s requires registration within 45 days of activation and a continuous internet connection.
Check the manufacture date on the battery as well. Fox ESS’s warranty, for example, runs 120 months from installation but no more than 125 months from manufacture for its EP batteries, so one that sat in a warehouse has a shorter warranty than the headline.
6. Switching tariff
The battery saves most on a time-of-use tariff, and switching is its own small process. Octopus Flux needs solar panels and an export meter number, which Octopus can apply for. Agile Octopus needs a smart meter. Some battery tariffs have stricter rules: Intelligent Octopus Flux is currently open only to customers who bought solar panels and a battery from Octopus. Check eligibility before the installation day so the battery is not left on a flat tariff for its first weeks.
What usually causes delays
- A G99 application, especially where the operator asks for an export limit or more information.
- The battery’s location. If the survey’s first choice fails PAS 63100, for example a loft or an escape route, the design changes.
- Missing documents for existing solar, such as the MCS certificate or inverter specification.
- Extra electrical work, such as a consumer unit upgrade, found at survey.
None of these is a reason to rush the comparison at the start. Two or three written battery storage quotes for the same specification, checked against the official prices, take less time than any of the delays above.
Questions people ask
How long does it take to install a home battery?
The work on site is usually one day. Tesla says a typical Powerwall installation takes a full day, with the power off for four to six hours, or eight or more if extra electrical work is needed. The total time from accepting a quote depends mainly on whether the system needs a G99 application to the network operator before it can be fitted.
Do I need permission from the network operator for a battery?
Every battery that can export is reported to your network operator, but the route depends on size. Up to 16 A per phase, about 3.68 kW on a single-phase home counting every inverter, the installer fits it and notifies the operator afterwards under G98. Above that, the installer applies under G99 before installation, and the operator may approve it with an export limit.
Can I cancel after accepting a battery quote?
A contract agreed at home, online or over the phone normally carries a 14-day cancellation period under the Consumer Contracts Regulations 2013. If you ask for work to start inside those 14 days, you can be charged for work already done. Some installers, Octopus among them, also take a deposit they describe as non-refundable, so read the terms before you pay it.
What paperwork should I get after a battery is installed?
An MCS certificate if the installer is MCS certified, an electrical installation certificate that includes a PAS 63100 statement about the battery's location, confirmation that the work has been notified under the Building Regulations, the network notification or approval, and the warranty registration. Enphase, for example, requires registration within 45 days of activation.