Commercial battery storage installation FAQs

Physical installation is usually short: a few weeks on site for a behind-the-meter system. The programme is set by the network operator: the G99 application and connection offer can take months, and longer where the network needs reinforcement. Ask the installer to submit the G99 application at survey stage so the clock starts early, and, where the network is constrained, whether a G100 export/import limitation scheme would let the project proceed within the existing agreed capacity. A credible programme shows the DNO milestone as the critical path.

That caution is reasonable, and it is why the design should follow the references written for commercial systems: the IET Code of Practice for Electrical Energy Storage Systems, BS EN/IEC 62619 for cell safety and BS EN/IEC 62933 for system safety, with NFCC guidance for larger sites. PAS 63100:2024 is written for dwellings, so it is context rather than the commercial standard. Lithium-iron-phosphate (LFP) cells are generally regarded as more thermally stable than NMC chemistry. Ask for the fire risk assessment, separation distances, detection and access arrangements in writing, and share them with your insurer before installation.

Often, yes. The tie-in to existing switchgear can usually be planned around operations, using temporary supplies, out-of-hours working or a short pre-agreed outage where one is unavoidable. The survey should establish the supply arrangement, available fault level and switchroom access so that the connection method is designed, method-statemented and risk-assessed before anyone arrives on site. Ask the installer how the tie-in will be done and how long any outage will last.

Often the battery is part of the answer to the constraint. A behind-the-meter battery with a G100 export/import limitation scheme can let a site add EV charging, heat pumps or production load while staying inside its existing agreed capacity, which may avoid or defer a DNO reinforcement. Whether the DNO accepts that approach is confirmed before final design, so ask for it in writing.

It should be clear in the contract. Many installers include the G99 application, single-line diagrams, protection settings, witness-test coordination and DNO liaison in their scope, along with any G100 design and the metering arrangement. If a quote leaves any of these out, you will be coordinating the DNO, the battery supplier and the electrical contractor yourself, so ask for the scope to be itemised.

A proper install ends with documented, witnessed commissioning: protection and control settings verified, G99/G100 functions demonstrated, metering and monitoring proven, and an O&M and handover pack issued. Where the DNO requires witness testing it is coordinated with them. Ask for the test results, the settings schedule, the fire and electrical certification and the O&M plan, which are the records your insurer and auditor will ask for.

Physical installation is usually a few weeks on site for a behind-the-meter system. The overall programme is set by the network operator: the G99 application and connection offer can take months, and longer where the network needs reinforcement. Getting the G99 application in at survey stage starts that clock early, and a G100 limitation scheme can sometimes let a project proceed sooner. Grid-scale standalone projects take much longer once planning is included.

G99 is the Energy Networks Association engineering recommendation for connecting generation and storage above 16 A per phase, which covers almost every commercial battery. The DNO reviews the connection, may require a network study, and sets the protection and metering requirements. Because network capacity is limited in many areas, the study and connection offer are usually the longest item on the programme. The installer normally prepares the application, single-line diagrams and protection proposals, and, where the network is constrained, may propose a G100 export/import limitation scheme so the site can connect within its existing agreed capacity.

It comes down to space, capacity and fire strategy. A containerised outdoor system is usually the fastest route to multi-MWh capacity and keeps the fire and space constraints outside the building, but it needs prepared hardstanding, separation distances and firefighting access. An indoor cabinet suits smaller systems at sites with a suitable plant room or switchroom, but the room must be compartmented, ventilated and fire-detected. A survey should assess both against the available space, target capacity and insurer requirements.

For commercial systems the main references are the IET Code of Practice for Electrical Energy Storage Systems, BS EN/IEC 62619 for cell safety and BS EN/IEC 62933 for system safety, with NFCC guidance for larger and grid-scale sites and your insurer's own requirements. PAS 63100:2024 is written for battery systems in dwellings, so it is useful context rather than the commercial standard. Lithium-iron-phosphate (LFP) cells are generally preferred for thermal stability. A fire risk assessment should be produced, and the insurer engaged, before installation.

Usually the installer, but check the contract. The G99 application, single-line diagrams, protection settings, metering arrangement, DNO liaison and witness-test coordination (plus any G100 limitation design) are often included in an installer's scope. If they are not itemised in the quote, you may end up coordinating a battery supplier, an electrician and the DNO yourself.

In most cases, yes. The tie-in to existing switchgear can be planned around operations using temporary supplies, out-of-hours working or a short pre-agreed outage where one is unavoidable. The survey should establish the supply arrangement, available fault level and switchroom access so that the connection method is designed, method-statemented and risk-assessed before installation starts.

Published UK ranges for 2026 put a 100 kWh commercial battery at about £20,000–£40,000 installed and a 200–500 kWh system at about £80,000–£250,000 or more (roughly £300–£500 per kWh). Systems up to 50 kWh cost more per kWh (about £400–£800), and containerised systems of 500 kWh and above fall to around £140–£240 per kWh, so a 1 MW / 2 MWh container works out at roughly £280,000–£480,000 before major grid works. These are budget ranges, not quotes. Cost depends on the power-to-energy ratio, switchgear and protection works, siting and civils, fire safety and any grid-connection contribution. On tax, the Annual Investment Allowance covers up to £1m of qualifying spend a year; above that the treatment depends on how the battery is classified, so confirm it with your adviser.

By survey, not by rule of thumb. Power (kW) is sized to the peak to shave or the load to support; energy (kWh) to how long that peak lasts. Many behind-the-meter systems are specified at one to two-and-a-half hours (for example 250 kW / 500 kWh). A competent installer analyses at least 12 months of half-hourly meter data, confirms the incoming supply capacity and available fault level, and settles the connection route before specifying plant, because the DNO position can change the design.

Commissioning is a documented, witnessed handover: protection and control settings verified, G99/G100 functions demonstrated to the DNO where required, metering and monitoring proven, and cell/thermal management confirmed. At the end you should hold the test results, the settings schedule, the electrical and fire certification and a planned O&M regime, which are the records your insurer and auditor will expect.

Yes. The battery should be sized to the measured daytime export surplus, then AC- or DC-coupled to the existing inverter and metering. A G99 variation (or new application) is usually needed for the added storage, with G100 limitation to stay within the existing agreed export capacity. How much more of the solar output is used on site depends on the surplus and the load profile, so ask for the estimate to be worked from your own half-hourly data.

It depends on the size and siting of the enclosure and on where the site is: England, Wales and Scotland have different planning rules, and listed-building or conservation-area constraints can apply. Larger containerised and standalone systems increasingly need full planning permission and fire-and-rescue consultation under NFCC guidance, with attention to separation, access and noise. Confirm the route with the local planning authority before any plant is ordered.

G100 is the Energy Networks Association engineering recommendation for customer export (and import) limitation schemes that hold a site within its agreed import/export capacity. It is used where the DNO connection is constrained: it can let a battery, and often new EV charging or production load, connect and operate without waiting for a network reinforcement, if the DNO accepts it. The limitation and its protection should be tested and demonstrated at commissioning.

Ask for competent-person registration (NICEIC, NAPIT or ELECSA, searchable on one register), MCS certification where it applies to your system and its size, and evidence of G99/G100 applications taken through your DNO. Check that the design follows the IET Code of Practice for Electrical Energy Storage Systems and BS EN/IEC 62619/62933. For container and larger installs, ask who takes the CDM 2015 principal-contractor role. Asking to see a commissioning pack and a fire risk assessment from a comparable job is a good test.

Behind-the-meter control and settlement depend on accurate half-hourly measurement. The CT and metering arrangement should let the control system see site import, export, generation and the battery correctly, and any meter change is coordinated with the supplier or meter operator. Getting the measurement design right at installation is what makes peak-shaving and G100 limitation work in service.

A planned O&M regime: remote monitoring with alerts, periodic electrical inspection, firmware updates, thermal-management and cell-balancing checks through the battery management system, and fire-system checks. O&M agreements are often aligned to the cell warranty period. Check whether software optimisation of charge and discharge is included, because tariffs and DUoS bands move over the life of the system.

Commercial LFP cells are commonly warranted to a stated number of cycles or years down to a stated share of retained capacity; the exact terms vary by manufacturer, so read the warranty document rather than a summary. A good proposal sizes the system with end-of-life capacity in mind, shows the warranted cycle count and degradation assumption, and says whether augmentation (adding cells later) is planned.

Often, yes. Rapid and ultra-rapid chargers create short, severe demand spikes that can trigger a grid upgrade. A battery can buffer those spikes, charging off-peak and from any on-site solar, so more chargers fit on the existing connection, and a G100 scheme can hold the combined site within its agreed capacity. Compare the cost against the DNO's reinforcement quote before deciding.