Commercial Battery Storage: When It Adds Value to Your Solar

Does my business need a battery with solar?

A hotel, pub, care home or farm that works into the evening fits the left-hand column more often than an office that shuts at 5pm. The installer tells you which applies from your own data.

How a battery uses your half-hourly data

Half-hourly data shows what the site uses in every half hour of the year. Lay the solar system's expected output over it and two things appear: the surplus the panels make that the site doesn't use, and the demand after the sun goes down. A battery is sized to move one into the other.

Each unit moved is worth the gap between what you pay and what you would earn exporting it, less what is lost charging and discharging. DESNZ's figure for a small business in the second quarter of 2026 was 28.6p per kWh including the Climate Change Levy (DESNZ); export rates are set by suppliers and must be above zero (Ofgem), and our examples use 4.1p. Ask your supplier for 12 months of half-hourly data before the survey.

Peak shaving and capacity charges

"Peak shaving" means using the battery to cut the site's demand at its most expensive or highest moments. Whether it saves you money depends entirely on how your supply is charged:

• Time-of-day rates. If units cost more in some periods, a battery charged from solar or cheaper periods can cover them.
• Charges for maximum demand or capacity. If part of your bill depends on your highest demand or an agreed capacity, a battery can lower the peaks it is measured on.
• A flat rate. Peak shaving does nothing on a single unit price.

Check your bill, or ask your supplier, which of these applies before you count on it. We don't publish battery savings: they depend on the tariff and the site.

Batteries and export limits

Most business systems are above 16A per phase, so they need the network operator's approval under G99 before connecting (NGED; smaller ones notify under G98, NGED). NGED's G99 forms cover electricity storage alongside generating equipment, so the battery goes in the same application. Where the network can't take everything the system could export, the installer may propose limiting export. A battery can then store what would otherwise be wasted, which can make a larger solar system worthwhile. See commercial solar system sizes.

Fire safety and where a battery can go

If you control business premises you are the "responsible person" for fire safety, and must carry out a fire risk assessment and review it regularly (GOV.UK). A battery is a change to the premises, so:

• Ask where and why. The installer should explain the proposed location, ventilation, separation from escape routes and how it is isolated.
• Update the fire risk assessment. Tell whoever carries it out before the battery goes in.
• Tell your insurer. Some insurers have their own requirements for batteries and solar; ask before you sign.
• Plan for access. Who can reach the isolators in an emergency, and what signage the site needs.

Adding a battery later, and tax

Many businesses fit solar first and add a battery once they can see their real export pattern. If you might, say so at the survey: the inverter, switchgear, wall space and the grid application can allow for it, which is cheaper than changing them later. Adding storage later may need the network operator's agreement again.

On tax, HMRC's guidance designates solar panels as special rate plant but doesn't mention batteries (CA22335), so ask your accountant how a battery is treated. See capital allowances on solar panels.