Commercial battery storage in the UK: a buying guide

Commercial battery storage is a battery system installed on a business’s side of the electricity meter. It stores power and releases it when it is worth more: through a weekday peak, after a power cut, or when the site’s own solar is not generating. It is bought by sites with a real load, such as factories, warehouses, farms, offices and hotels, and it is a different product from a household battery, with different rules and a different price.

What commercial battery storage is, and what it is not

A commercial system is a battery energy storage system (BESS) sized for a business: from a cabinet of a few tens of kilowatt-hours in a plant room to a containerised unit of a megawatt-hour or more. Our guide to what a BESS is explains the parts, and the technical guide to commercial BESS covers how they work in more depth.

Three things are often confused with it:

• A household battery. The technology is the same, but the supply, the connection process, the standards and the tax treatment are different, and household schemes do not apply to a business.
• Grid-scale storage. These are large batteries connected directly to the network that trade electricity. A business battery sits behind its own meter and serves one site.
• A UPS or a generator. A UPS bridges seconds or minutes, and a generator makes power from fuel. A battery can do part of either job only if it is designed for it, which means holding back a reserve.

You will see the same product called commercial, industrial, or C&I storage. The words vary by supplier and the equipment is the same kind. Larger industrial sites tend to need bigger systems.

What a business battery does

A commercial battery does one thing, which is to move electricity in time, and a site gets value from it in a handful of ways. Which ones apply depends on the site, and each is explained on its own page:

• Peak shaving: discharging at the site’s peak to cut the charges that follow demand, including DUoS charges and the capacity the site pays for.
• Energy arbitrage: charging when power is cheap and using it when it is dear, on a time-of-use tariff.
• Storing solar: using more of the site’s own generation instead of exporting it at a low price.
• Backup power: keeping chosen loads running when the grid fails, which only works if the battery holds a reserve.
• Grid services: payments for flexibility through a supplier or an aggregator, where the site qualifies. They depend on delivery and are never guaranteed.

A battery sized for one job may do another badly. A system set up to shave a peak, for example, may not hold enough reserve for backup, so decide what the battery is for before you size it.

Does it suit your site? Six checks before you ask for quotes

These checks need a year of half-hourly consumption data, which your supplier or meter operator can provide. Our guide to reading half-hourly data shows how to read it.

1. Is your demand peaky? A battery shaves peaks that last a few hours. Compare your highest half-hour with your average: a flat, round-the-clock load leaves little to shift, and a spiky one is where a battery works hardest.
2. What do you pay for peaks? Look at the time bands on your tariff, the network charges, and any charge for the capacity you have agreed. The DUoS page explains the network element.
3. Do you generate your own power? If the site has solar and exports at a low price, storing the surplus can raise how much of it you use yourself. Read solar-plus-storage and, if the array already exists, how AC- and DC-coupled batteries differ.
4. What does an outage cost you? If a power cut stops production or spoils stock, a battery can carry a defined load, but it needs to be sized for the reserve, not only for savings.
5. Is your connection a limit? If you cannot add chargers, plant or generation because of the capacity you are allowed, a battery can help, but the network operator decides. Read the G99 guide early, because the application can set the programme.
6. Can you commit? A battery is a long-life asset. A short lease, a site you may leave, or no budget for the connection works all weigh against it.

If most answers are no, a battery probably will not pay its way on your site, and a good adviser will tell you so. If several are yes, the next step is to size it from your own data, not from a rule of thumb.

How big should it be? Power and energy

A battery is specified by two numbers. Power, in kW, is how fast it can charge or discharge. Energy, in kWh, is how much it can hold. They answer different questions: a peak is a power problem, a long outage is an energy problem, and buying the wrong one is a common and expensive mistake. Our guide to kW vs kWh explains the difference and shows how long a given battery can carry a given load.

What commercial battery storage costs in the UK

The most recent published UK bands, from Reonic’s July 2026 cost guide drawing on Heatable and GSL Energy, are these. They come from different sources and overlap, and the per-kWh figure falls as systems get bigger.

What moves a quote within those bands is rarely the cells. The US National Renewable Energy Laboratory prices a commercial battery as an energy part (per kWh) plus a power part (per kW) plus a fixed amount, which is why a system with more kW for the same kWh costs more. In practice the connection works, switchgear, enclosure, fire design, controls and warranty terms are what separate one quote from another. Our cost guide has the full bands, a worked arithmetic table and a calculator that does the sums on your own figures, and the guide to comparing quotes shows how to put bids on the same footing.

The UK rules in one place

Most pages on this subject skip the rules. These are the ones that apply to a commercial battery in the UK, with where each is explained. This is general information, not legal or tax advice, and your installer, network operator and accountant will give the answer for your site.

From first look to a working system: the steps

1. Get the data. Ask for a year of half-hourly consumption and, if you have solar, its generation.
2. Decide what the battery is for. Peak shaving, solar, backup, a constrained connection, or a mix. This sets the size.
3. Check the connection. Find your network operator and ask how a G99 application would be treated for your site and what timescale it quotes. Do this before you sign anything, because it can set the programme.
4. Get comparable quotes. Ask each bidder for nominal and usable energy, continuous power, scope, exclusions and warranty in writing. Our quote checklist sets out the questions.
5. Read the warranty. Check the years, the capacity guaranteed at the end and any limit on throughput. See what the published warranties promise.
6. Settle planning, insurance and the tax treatment. Planning if it is outdoors, your insurer before energisation, and your accountant on VAT and allowances.
7. Install and commission. For a G99 Type A installation, the ENA guide says the network operator may choose to witness the tests, in which case the scope, time and date go to it at least 15 days beforehand; if it does not, the Installation Document and the test results are due within 28 days of the tests being completed. For Types B to D the network operator needs the test details at least 28 days before the proposed commissioning date.
8. Operate and review. Check the first months of half-hourly data against what the battery was bought to do.

Common mistakes

• Buying on price per kWh alone. Two quotes at the same price per kWh can describe different batteries, because the kWh may be nominal in one and usable in the other.
• Sizing for energy when the problem is power. Shaving a peak needs kW first.
• Leaving the connection until last. The network operator’s timescale is out of your hands.
• Assuming household incentives apply. They do not, including the 0% VAT relief.
• Taking a headline saving as a forecast. Savings come from your own load and tariff, not from a general figure.
• Skipping the data. Without half-hourly data every number, including a supplier’s, is a guess.

The same findings appear in our audit of what UK commercial battery pages leave out: of the eight explainer pages we could read, none quoted a price and none mentioned capital allowances.