What it is and how it works

A battery stores electricity and gives it back later. On a commercial site it does that for two reasons: price and timing.

Price, because most business supply contracts charge different rates at different times. A battery charges when power is cheap and runs the building when it is dear. Timing, because solar makes most of its power in the middle of the day, and plenty of buildings are still drawing load long after that. Without storage, the surplus goes out to the grid at an export rate well below what you pay to buy power back in the evening.

The battery sits alongside your existing supply, with an inverter or gateway and its own protection. A control system decides when to charge and when to discharge, and it reports what it did. Capacity is measured in kilowatt hours, written kWh, and the speed it can charge or discharge is measured in kilowatts, written kW. Both matter: a large store that can only discharge slowly will not flatten a sharp peak.

Cost, VAT and allowances

We quote a fixed price after the survey, itemised across the battery, the inverter or gateway, the electrical work, the protection and the commissioning. We do not publish payback figures, because they depend entirely on your own contract.

VAT. The zero rate for energy-saving materials does not extend to commercial premises, so the standard rate applies. A VAT registered business usually recovers it.
Capital allowances. Battery storage is plant and machinery. The Annual Investment Allowance is £1 million a year and covers most plant and machinery for companies, sole traders and partnerships of individuals. Where a battery is installed as part of a solar scheme, parts of the spend may fall into the special rate pool instead, which writes down at 6% a year, and a company may be able to claim a 50% first-year allowance on that. The split is a question for your accountant.

Figures reviewed 20 September 2026.

What a battery will not fix

A battery moves energy in time. It does not make energy, and it does not reduce what the building uses. If your tariff is flat, there is no gap for it to work in. If your peak is long and heavy, the battery needed to cover it may cost more than the peak does. If the roof is already sized to your daytime load and you export very little, storage adds less than it would on a site that exports a lot.

We say this at the survey rather than after. Where the numbers do not work, the honest answer is usually to fix the load or the contract first, and revisit storage afterwards.

Storage with the rest of the site

A battery earns most next to other things. With commercial solar it keeps the midday surplus on site. With workplace EV charging it can take the edge off a bank of chargers all pulling at once. With air conditioning it covers the afternoon peak on the hottest days. Our design and consultancy work models those together before anything is ordered.

Pros and cons

Pros

Charges when power is cheap or the roof is producing, and discharges when it is dear
Raises how much of your own solar you use on site instead of exporting it at a lower rate
Can hold a site through short interruptions if it is designed to, which matters where a stoppage costs money
Capital allowances apply in the same way as other plant and machinery
Can be added to an existing commercial solar system without replacing the array

Cons

The 0% VAT rate for energy-saving materials does not reach commercial premises, so VAT is charged at the standard rate
The case rests on the gap between the price you charge at and the price you avoid, and that gap moves with your contract
A flat tariff with no cheap window gives a battery very little to work with
It needs floor or wall space with clearance, ventilation and a sensible fire separation, which not every plant room has
Your network operator has to approve it, and the answer can carry conditions
Backup is a design decision, not something every battery does by default

Who it suits

Sites already running commercial solar that export a meaningful share of what they generate
Businesses on a time-of-use contract with a real difference between peak and off-peak rates
Buildings with a sharp, predictable demand peak that sits in the expensive part of the day
Sites where a short power interruption stops production, spoils stock or closes the doors
Fleet depots charging vehicles overnight alongside a daytime solar array

What is included in a Bespoke installation

A survey of the plant room or proposed location, the incoming supply, the switchgear and the metering
Analysis of your half-hourly data and your current contract, so the battery is sized to the pattern you actually have
A written position on what the battery will and will not do in a power cut
The network operator application, and any conditions it comes back with
Supply and installation of the battery, inverter or gateway, protection and metering
Commissioning, the control settings explained, monitoring set up, and the operation and maintenance file

Frequently asked questions

Is there 0% VAT on a commercial battery?

No. The zero rate for installing energy-saving materials applies to residential accommodation and to buildings used solely for a relevant charitable purpose, and HMRC's notice states that the standard rate applies elsewhere. A battery in a commercial building is charged VAT at the standard rate, which a VAT registered business usually recovers in the normal way.

Will a battery keep us running in a power cut?

Only if it is designed to. Backup needs the right inverter or gateway, a separate protected circuit and a decision about which loads are worth holding up. That changes the cost, so we ask the question at the survey rather than assume. Tell us what stopping actually costs you and we will size it against that.

Can we add a battery to solar we already have?

Usually, yes. It depends on the existing inverter, the switchgear and the space. Some systems take a battery directly, others need a battery with its own inverter alongside. We check all three at the survey before quoting.

How do you size a commercial battery?

From your half-hourly consumption data and your supply contract, not from the size of the solar array. We look at how much power the peak period actually draws, how long it lasts and what it costs, then size the battery to the part of that you can economically shift.

What about fire safety and where it goes?

A commercial battery needs a location with clearance, ventilation and separation from what is around it, and the answer differs between a plant room, a warehouse and an outdoor enclosure. We agree the location at the survey and set it out in the design, along with anything your insurer will want to see.