Commercial battery storage: sizing, grid connection and fire safety

Business electricity is usually metered half-hourly, and that data is the basis of any serious proposal. It shows when demand peaks, how often, and how much of it a battery could shift. Ask your supplier or meter operator for at least a year of it before inviting proposals. A supplier that sizes a commercial battery without it is guessing.

The same data shows whether storage is the right tool at all. Sometimes shifting a process, staggering start-up of machinery or changing the tariff saves more than a battery would.

• reduce peak demand so the site stays within its agreed grid capacity
• store rooftop solar generated at weekends or lunchtimes for use when the site is busy
• support electric vehicle charging without a larger grid connection
• keep critical loads such as refrigeration, servers or alarms running during an outage
• earn income from flexibility services, where a site and its supplier are eligible

Any battery that can export, or that is large enough to affect the local network, needs the distribution network operator's approval before it is connected. For larger systems the study can take months and may result in an export limit or a requirement for protection equipment. Ask each supplier to state who submits the application, when, and what happens to the programme if the answer comes back with conditions.

Containerised or outdoor systems may also need planning permission, especially near homes or in protected areas. The supplier should tell you early whether it expects an application and who prepares it.

In England and Wales, the Regulatory Reform (Fire Safety) Order 2005 makes the responsible person for business premises accountable for fire risk. A large lithium battery changes that risk, so the fire risk assessment has to be reviewed before installation, not afterwards. Location, separation from escape routes and other buildings, detection, ventilation and access for the fire service all belong in the design.

Tell your insurer before you order. Insurers increasingly ask for specific information about battery chemistry, location and monitoring, and an uninsurable installation is an expensive surprise.

Source: legislation.gov.uk

• the load data used and the modelled savings, month by month
• usable capacity, power rating and expected degradation over the warranty
• the connection application and any assumed export limit
• fire safety design, including the standards followed
• monitoring, remote support and response times for faults
• maintenance obligations and what voids the warranty
• decommissioning and recycling at end of life

The zero rate for batteries under the energy-saving materials rules applies to installations in homes and certain residential or charitable buildings. For ordinary business premises, assume standard-rated VAT and ask your accountant how it and any capital allowances apply to your organisation.

Some suppliers offer the battery as a service or under a shared-savings contract. Read how savings are measured and what happens if your usage changes, because that determines what you actually pay.

Describe the site, the reason for storage and any existing solar. The request is offered anonymously to storage suppliers covering your region, and exactly one can buy it. We email you its company name, address and phone number before it receives your details. The service is free for you, and nothing obliges you to accept a proposal.