Commercial battery storage installation FAQs

Physical installation is short, typically 1-6 weeks on site for a behind-the-meter system. The programme is set by the DNO: a G99 study and connection can run 3-18 months depending on network capacity in your area. We submit the G99 application alongside the survey so the clock starts on day one, and where the network is constrained we engineer a G100 export/import limitation scheme so the project can proceed inside your existing agreed capacity rather than waiting for reinforcement. We give you a programme with the DNO milestone shown honestly as the critical path.

So are we, which is why we design to the standards that address exactly that: PAS 63100:2024 principles for installation and fire protection, BS EN 62619 for cell safety, BS EN/IEC 62933 for system safety, and NFCC guidance for larger sites. We use lithium-iron-phosphate (LFP) cells, which are far more thermally stable than older NMC chemistry, and design in separation distances, firefighting access, detection, thermal monitoring, and appropriate bunding or compartmentation. We produce the fire risk assessment and engage your insurer and, where needed, the fire authority before we install, not after.

In most cases yes. We plan the tie-in to your existing switchgear around your operations, using temporary supplies, out-of-hours working, or a short pre-agreed outage window only where it is unavoidable. The survey establishes your supply arrangement, available fault level, and switchroom access up front so the connection method is designed, method-statemented, and risk-assessed before we are on site. Minimising disruption is an engineering decision we make at design stage, not something we improvise on the day.

Often the battery is the answer to the constraint, not a casualty of it. A behind-the-meter battery with a G100 export/import limitation scheme can let you add EV charging, heat pumps, or production load while staying inside your existing agreed capacity, avoiding or deferring a costly DNO reinforcement and a long connection queue. We confirm the approach with your DNO before final design and engineer the limitation and protection to hold the site within its agreed limit, typically reacting within 15 seconds.

We handle it. The G99 application, single-line diagrams, protection settings, witness-test coordination, and DNO liaison are part of our scope, along with the G100 limitation design where it is needed and the half-hourly metering arrangement. You get one accountable contractor for the survey, design, connection application, install, and commissioning, rather than being left to project-manage a battery supplier, an electrician, and the DNO yourself.

Every install ends with a 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 we coordinate it. You receive the test results, the settings schedule, the fire and electrical certification, and a planned O&M regime, so the system is demonstrably compliant and you have the records your insurer and auditor will ask for.

Physical installation is typically 1-6 weeks on site for a behind-the-meter system. The overall programme, however, is set by the DNO: a G99 study and connection can run 3-18 months depending on network capacity in your area. We submit the G99 application alongside the survey so the clock starts immediately, and use a G100 limitation scheme where it lets the project proceed sooner. Grid-scale standalone projects run 18 months to several years including planning.

G99 is the Energy Networks Association connection agreement required for storage above 16 A per phase, which covers almost every commercial system. 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. We prepare the application, single-line diagrams, and protection proposals, liaise with the DNO, and, where the network is constrained, engineer 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 (roughly 60-500 kWh) at sites with a suitable plant room or switchroom, but the room must be compartmented, ventilated, and fire-detected. We assess both against your available space, target capacity, and insurer requirements at the survey.

We design to PAS 63100:2024 principles for installation and fire protection, BS EN 62619 for cell safety, and BS EN/IEC 62933 for system safety, with NFCC guidance for larger and grid-scale sites. We specify lithium-iron-phosphate (LFP) cells for their thermal stability, and engineer separation distances, detection, thermal monitoring, and appropriate compartmentation or bunding. A fire risk assessment is produced and the insurer, and where necessary the fire authority, engaged before installation.

We handle it as part of our scope: the G99 application, single-line diagrams, protection settings, half-hourly metering arrangement, DNO liaison, and witness-test coordination, plus the G100 limitation design where the network is constrained. You get one accountable contractor across survey, design, connection, install, and commissioning rather than having to coordinate a battery supplier, an electrician, and the DNO yourself.

In most cases yes. The tie-in to your existing switchgear is planned around your operations using temporary supplies, out-of-hours working, or a short pre-agreed outage only where unavoidable. We establish your supply arrangement, available fault level, and switchroom access at survey so the connection method is designed, method-statemented, and risk-assessed before we mobilise. Minimising disruption is a design-stage decision, not an on-the-day improvisation.

As a 2026 rule of thumb, fully installed behind-the-meter commercial BESS lands at roughly £400-£700 per kWh of usable capacity, falling toward £250-£400/kWh at multi-MWh scale. A 250 kW / 500 kWh system is around £150,000-£300,000; a 1 MW / 2 MWh system £600,000-£1.2m. Cost depends on power-to-energy ratio, switchgear and protection works, siting and civils, and any grid-connection contribution. Qualifying plant attracts 100% AIA on the first £1m and a 50% first-year allowance on the balance.

By survey, not by rule of thumb. Power (kW) is sized to the peak you need to shave or the load you need to support; energy (kWh) to how long that peak lasts, most behind-the-meter systems land at 1.5-2.5 hours (e.g. 250 kW / 500 kWh). We pull at least 12 months of half-hourly meter data, confirm your incoming supply capacity and available fault level, and settle 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. You receive the test results, settings schedule, electrical and fire certification, and a planned O&M regime. The system is demonstrably compliant and you hold the records your insurer and auditor will expect.

Yes, and it is one of the most common installs we do. We measure your existing daytime export surplus and size the battery to it, then AC- or DC-couple the storage to your existing inverter and metering. A G99 variation (or new application) is usually needed for the added storage, with G100 limitation to stay within your existing agreed export capacity. Adding storage typically lifts self-consumption from 40-60% toward 80%+.

Behind-the-meter enclosures on an existing commercial site are often permitted development or a minor application, subject to size, siting, and listed-building or conservation-area constraints. Containerised and larger standalone systems increasingly need full planning permission and fire-and-rescue-service consultation under NFCC guidance, with attention to separation distances, firefighting access, and noise. We confirm the planning route in the feasibility study before any plant is ordered.

G100 is an export (and import) limitation scheme that holds a site within its agreed Maximum Import/Export Capacity, typically reacting within 15 seconds. We install one where the DNO connection is constrained: it lets a battery, and often new EV charging or production load, connect and operate without a costly network reinforcement or a long queue. The limitation and its protection are engineered, tested, and demonstrated at commissioning.

Look for MCS commercial certification for the storage element, NICEIC or NAPIT electrical registration, demonstrable G99/G100 experience across UK DNOs, and design to BS EN 62619, BS EN/IEC 62933, and PAS 63100:2024. For container and larger installs, CDM 2015 principal-contractor competence and ISO 9001/14001/45001 matter. Ask to see a commissioning pack and a fire risk assessment from a comparable job, that is the real test of an installer versus a broker.

Behind-the-meter control and settlement depend on accurate half-hourly measurement. We design the CT and metering arrangement so the control system sees site import, export, generation, and the battery correctly, and coordinate any meter change with your supplier or meter operator. Getting the measurement design right at install stage is what makes peak-shaving and G100 limitation actually work in service.

A planned O&M regime: remote 24/7 monitoring with automated alerts, periodic electrical inspection, firmware updates, thermal-management and cell-balancing checks via the battery management system, and fire-system checks. Most clients sign a 10-year-plus O&M agreement aligned to the cell warranty. Software-led optimisation of when to charge and discharge is usually included so the system keeps capturing value as tariffs and DUoS bands move.

Quality LFP commercial cells are typically warranted for around 6,000-10,000 cycles or 10 years to roughly 70% retained capacity, with real-world life often longer. We size with end-of-life capacity in mind so the system still meets its target late in life, and plan augmentation (adding cells) where it makes sense. The warranted cycle count and degradation curve are stated in every proposal.

Yes, and it is often the cheapest way to add chargers. Rapid and ultra-rapid chargers create short, severe demand spikes that can trigger an expensive grid upgrade. A battery buffers those spikes, charging off-peak and from any on-site solar, so more chargers fit on your existing connection. We design the storage, protection, and charging infrastructure together and hold the combined site within its agreed capacity with a G100 scheme.