Home Power
Advisor ROI calculator

System finder

What do you want to power, and for how long?

Answer four questions, tick your appliances and set the hours. The finder works out the battery size and shows the systems that fit.

1. About you
Where is the system for?
What matters most?
When the power fails, how should it take over?
Installation

Slide left to set a ceiling. Fully right means no limit.

2. What you want to run

Tick what you want to run and set how many (×). Watts (W) are typical running figures: change them to match the rating plate on your own appliance. Daily energy allows for the time each one is actually running.

 

0 appliances selected  

3. How long without the grid

From 1 hour to 4 days, with no charging in between.

–used over 24 hours
–battery size to look for
–peak power to allow for
–used per 24 hours

Battery size allows 10% for inverter losses. Peak power is everything that runs continuously plus your single largest appliance.

Systems and batteries that fit

Everything that fits

Loading systems…

Reading the results

  • Our picks are the lowest price, the best value per kWh and the closest fit among products that suit your answers, are in stock and can supply your peak power.
  • Price is the advertised hardware price including VAT, checked on 12 November 2026. Each result says what the price covers. Installation, delivery and backup wiring are usually extra.
  • kWh usable or nominal. Usable is what you can draw. Nominal is the label figure and is a little higher. Compare like with like.
  • Price per kWh is the price divided by storage. Battery-only products look cheapest because the inverter is extra.
  • Automatic on wired backup circuits means the inverter takes over by itself for the circuits an installer connects to its backup output.

Limits of this tool

The finder sizes storage. It does not design a system. Before you buy, an installer or supplier should confirm that the inverter can start your largest motor, that the battery works with the inverter, and that the installation meets wiring and network rules.

We list products we can find current UK prices for. It is not every product on the market. A listing or a pick is a starting point for your own checks, not a recommendation to buy: confirm the exact model, what is included and the warranty with the seller.

Ask us about a system that is not listed