There are three broad answers, they solve different problems, and the wrong one is expensive in ways that only appear later.

UPS

A battery that carries a small load for a short time. Its job is to keep the till, the router and a computer alive, or to give equipment time to shut down safely.

Cheap, silent, needs no installation, and it will not run a kettle. For a business whose main loss is being unable to take payment or answer email, this is frequently the entire answer and costs very little.

Inverter and batteries

A larger battery system that runs selected circuits for several hours. Silent, no fuel, low maintenance, and it recharges when the power returns.

The battery is the cost and the consumable — it has a finite life measured in cycles and will need replacing, which belongs in the sums from the start. Sizing is a trade-off between how much you run and for how long, and this is where an honest load calculation pays for itself.

It suits most offices, shops and small premises, where the loads are modest and the outages are a few hours.

Generator

Runs large loads for as long as you feed it. The answer where there is real machinery, refrigeration at scale, or an operation that cannot pause.

It is noisy, needs fuel and servicing, requires safe placement and ventilation, and needs correct switching so it can never feed back into the grid — which is a safety matter and a job for a qualified electrician, not an extension lead.

Solar, with or without batteries

Solar reduces your bill. Solar with batteries also keeps you running during an outage — panels alone generally do not, because a grid-tied system shuts down when the grid does.

That distinction catches people out regularly. If continuity is the objective, the battery is the part doing the work and the panels reduce what it costs to charge it.

What to check before buying

  • Get the load assessed by somebody qualified rather than estimating.
  • Ask for a certificate of compliance for the installation, and keep it — your insurer may ask.
  • Confirm what the batteries are warranted for, in cycles as well as years.
  • Ask what happens when it fails, who services it, and how long a replacement takes.
  • Get more than one quote, and compare what is actually included rather than the headline.

Tell your insurer

An installation changes the risk at the premises, and an uncertified one can affect a claim that has nothing to do with power. It is a phone call and it removes a problem you would otherwise only discover at the worst moment.

General guidance, not technical, electrical or financial advice. Installations must be done by a qualified person and certified.