Business battery storage: how it works and when it pays back

A business battery is a bank of rechargeable cells, usually lithium-ion, that sits behind your meter. It charges when power is cheap, or when your own solar is producing more than you use, and it discharges when power is dear or the grid is down. For a typical small business it is an add-on that only pays back in particular circumstances, not a default upgrade.

What a battery can and cannot do for your bill

A battery does not make energy cheaper. It moves your purchases around in time. That helps only if the price you pay, or the charges you face, differ across the day. Four uses come up most often:

• Time-shifting. Charge overnight or at weekends on a cheaper night rate or time-of-use tariff, and use that stored power during the day.
• Solar self-consumption. Store midday solar you would otherwise export for little, and use it in the evening. See commercial solar panels and the Smart Export Guarantee for what exports earn.
• Peak shaving. If you have a half-hourly meter and pay for capacity, a battery can cover short spikes so your highest demand stays lower. This links to supply capacity and kVA charges.
• Back-up. Keeping a till, chiller or server running through a short outage. This is resilience, not a saving.

A flat-rate tariff with no solar and no capacity charge gives a battery very little to work with.

Do you have the right kind of tariff and meter?

Most small businesses buy on a single unit rate plus a standing charge. With one flat rate, charging at night saves nothing. You need either a day and night split (see day and night rates), a supplier offering time-of-use pricing, or a half-hourly meter so that your usage is recorded in 30-minute blocks. Ask any supplier whether the tariff you are quoted rewards shifting before you spend a penny on hardware.

A worked example: what time-shifting is really worth

This example uses assumed prices, not a quote. Say your tariff has a night rate of 15p/kWh and a day rate of 30p/kWh, and you buy a battery with 40 kWh of usable storage that returns 90% of what you put in.

1. Energy you use from the battery each working day: 40 kWh.
2. Energy you must buy to supply it: 40 ÷ 0.9 = 44.4 kWh, costing 44.4 × 15p = £6.67.
3. Day-rate energy you avoid buying: 40 × 30p = £12.00.
4. Daily saving: £12.00 − £6.67 = £5.33.
5. Over 250 working days: 250 × £5.33 = about £1,333 a year.

Now the cost. Installed prices vary widely by size, chemistry and site, so get written quotes. Work backwards instead: for time-shifting alone to repay within 10 years, the whole installed system would need to cost less than 10 × £1,333 = £13,330, or about £13,330 ÷ 40 = £333 per kWh of usable storage. Compare that ceiling with the quotes you receive and with the warranty length. Paybacks improve where solar surplus and a wide day/night price gap combine, but treat any installer's payback figure as a claim to test against your own bills.

Ask for the payback calculated from your own half-hourly or monthly usage, with the assumptions written down: tariff, round-trip efficiency, yearly capacity loss and maintenance.

Peak shaving and capacity charges

Where you pay a network charge based on your highest demand, shaving the peak can be worth more than shifting energy. If a piece of kit trips your demand above your agreed capacity for a few minutes in a month, you can be charged an excess for the whole month. A battery that covers those spikes removes the charge. This only applies to sites on half-hourly or maximum-demand arrangements; a small shop on a standard meter has no such charge to avoid.

Connecting it to the grid

Batteries count as energy storage under the grid connection rules, so your local network operator (the DNO) must be involved. Under the published connection procedures, storage rated above 16A per phase (3.68kW on a single-phase supply) falls under G99, where the application goes to the DNO before connection; only very small units use the simpler G98 notification route. Use a competent, accredited installer who will handle this, and check the following before signing:

• Fire safety and siting. Ask the installer and your insurer where the unit can go and what protection it needs.
• Your insurer's requirements, which can differ by building.
• Whether you own the building. A tenant needs the landlord's consent; see the landlord guide.
• Planning rules for outdoor units.

Who a battery tends to suit, and who it does not

More likely to make sense

• Sites with solar panels that export more than they use at midday, such as a school-hours workshop or a farm unit.
• Businesses on half-hourly meters with sharp, short demand peaks, for example welding, compressors or fast EV chargers (see workplace EV charging).
• Premises where an outage is costly: cold storage, a dental practice, a data-heavy office.

Less likely

• A shop or salon on a flat single-rate tariff with steady daytime use.
• Tenants on short leases who cannot take equipment with them.
• Anyone who has not yet fixed obvious waste such as lights and heating left on out of hours.

If you are unsure which group you are in, a sensible first step is an energy audit, which shows when and why you use power.

Costs that are easy to miss

• Capacity fades a few per cent a year, so year-ten savings are lower than year-one.
• Maintenance and monitoring software may be an annual fee.
• Round-trip losses, as in the example above.
• Supplier terms. Export rates vary between suppliers and tariffs; ask before relying on them.

Tax and VAT

The 0% VAT relief on installing energy-saving materials, which now includes batteries, applies to homes and to buildings used solely for relevant charitable purposes, not to ordinary business premises. A business should expect VAT at the standard rate, which it can usually reclaim if VAT-registered. For income tax or corporation tax, GOV.UK lists the Annual Investment Allowance of up to £1 million on qualifying plant and machinery; ask your accountant whether your battery qualifies before relying on it.

Cheaper steps to take first

Batteries multiply the value of efficiency, they do not replace it. Work through saving energy in a small business, consider LED lighting and look at energy monitoring first. Then check whether your contract and meter even allow a time-based tariff.

Next steps

1. Pull 12 months of bills or half-hourly data and note your day, night and peak usage.
2. Ask your supplier what time-of-use or export terms you could get.
3. Get at least two installer quotes with written payback assumptions.
4. Check landlord, insurer and network operator requirements before committing.

Biz Energy is independent and does not sell batteries or take commission.