Can a business battery keep your site running during a power cut?

A business battery can supply selected circuits during a power cut only if the complete installation supports backup operation. Ordinary grid protection disconnects generation when mains power fails [S1]. As an illustration, 40 kWh delivered to a steady 10 kW load lasts four hours; actual runtime depends on reserve and demand. Checked October 2026.

Last checked 16 October 2026

Will your business battery work in a power cut?

Start with the switching design. Buying storage for electricity trading does not establish that your site will have power when the network fails. The OPSS technical report explains that anti-islanding protection prevents a grid-connected battery feeding a failed network [S1]. Treat that as the starting point for a design discussion, rather than evidence of backup capability.

Ask the installer to mark every backed-up circuit on a drawing. Request the proposed isolation equipment, earthing arrangement and changeover behaviour. Ask what happens if the battery is empty when the outage starts. Get these answers in the specification before accepting a quote.

Separate the essential service from the whole building. Your priority might be refrigeration controls, payment terminals or communications. A proposed design should explain which circuits remain off. Compare this with commercial battery sizing.

How long could battery backup power your business?

Kilowatts (kW) measure power: how fast equipment uses energy. Kilowatt-hours (kWh) measure energy: how much is available over time. Both matter when describing an outage.

Here is an illustration, not a quote. Assume the system can deliver 40 kWh at its backup output after reserves, conversion losses and operating limits. Assume each load stays constant and is within the inverter’s capability.

These are calculated examples, not product ratings. A motor starting or a heater switching on changes the load. Ask for measured operating demand and starting demand, then repeat the calculation with the supplier’s usable energy at the required conditions.

Do the same exercise for an aged battery. For example, assumed delivered energy of 32 kWh at 10 kW gives 3.2 hours. That is a sensitivity test, not a forecast of degradation. Read battery warranty and degradation before selecting the reserve.

Does an office need uninterrupted power or emergency backup?

Write down whether each essential device can tolerate an interruption. An uninterruptible power supply, or UPS, and a larger storage installation are different procurement questions. Do not accept the word “backup” as a specification for computers, communications or sensitive process controls.

Require a stated transfer time and an acceptance test using the actual equipment. If your business needs an uninterrupted supply, ask the designer to document how that requirement is met. The OPSS report establishes the importance of inverter protection; it does not certify any proposed site’s changeover performance [S1].

Include operating instructions for staff. Who can isolate a faulty circuit? What should happen when the reserve falls? Who can restart equipment? Request a demonstration, a shutdown sequence and the location of emergency controls. Keep that information available during an outage.

Which circuits should stay on during an emergency?

Build a schedule with your facilities manager and the installer. For each item, record its purpose, running demand, starting demand, required operating time and tolerance for interruption. Use metered evidence where available, rather than adding equipment labels without checking how the equipment operates.

Ask for load shedding: a documented order for disconnecting less important circuits. Treat any interaction with a standby generator as a separate engineering task. Require the installer to confirm compatibility, protection and responsibility for testing the combined system.

Use battery fire safety to prepare questions about siting, access and emergency response. DESNZ’s storage guidance covers risk assessment across a system’s life. Its main scope is grid-scale equipment, so your designer must identify the requirements applicable to your smaller business installation [S3].

What grid, planning and site checks come before installation?

Your distribution network operator (DNO) manages the local electricity network. G99 is the engineering recommendation governing relevant generation connected in parallel with that network. National Grid Electricity Distribution includes energy storage in its connection procedures [S2]. Your installer should confirm the applicable route with your own network operator.

Ask for import and export limits, approved drawings and the commissioning evidence for the final design. A backup function does not establish permission for the system’s everyday grid-connected operation. Equally, a connection offer does not establish the runtime or switching performance of your backup.

Confirm the proposed cabinet location with your installer, insurer and, where necessary, council. Ask about emergency access, noise, flood exposure, building exits and maintenance space. Obtain landlord consent where your property arrangements require it. Check lease and liability wording with your solicitor.

How should you compare cost, funding and grants?

Request an itemised quote covering batteries, inverter, switching, essential-load wiring, controls, commissioning and maintenance. Ask for the extra price of backup functionality separately from ordinary bill-management storage. No verified standard backup premium or nationwide commercial battery grant is used here.

Compare fully funded, part funded and self funded proposals by the service you actually receive. Ask who controls the reserve, who pays for replacement and what happens when the equipment cannot provide the contracted backup. A trading-focused funded offer should not be assumed to include a resilience service.

Give outage protection its own decision record. Estimate interruption cost using your own stock, recovery labour and lost operating margin. State the assumed outage frequency and duration beside that estimate. Avoid presenting possible avoided loss as annual cash income. Discuss tax treatment with your accountant.

What should you prepare before enquiring?

Bring the essential-load schedule, recent consumption data, a site plan and your required runtime. Ask for a survey and a written test plan covering a mains failure, low reserve and restoration of normal supply. Browse the guide library for related design questions.

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