Commercial Battery Storage Installation: the Independent UK Guide

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.