Backup Hours: Power Cut Time
Work out how long the battery will last on the appliances you have actually got switched on.
Download on the App Store
Screenshots
Features
A figure while the power cut is still on
Storm brings the lines down and everyone asks the same thing: how long? Tick what is running and Backup Hours works out the hours the battery should manage on that load.
Enter the inverter details once
Capacity in amp-hours, system voltage, battery type — flooded, AGM, gel or LiFePO4 — and the depth of discharge you are prepared to allow. Every power cut after that is just ticking boxes.
Weigh up what to switch off
Untick the immersion heater and the remaining hours shift straight away, before you go anywhere near the switch. You decide what goes with a figure in front of you.
Kept on the Lock Screen
A Live Activity leaves the countdown where you can see it, so you are not unlocking the handset in a dark kitchen. A widget puts the same figure on the Home Screen.
Fitted to your battery, not the sticker
After three years a battery no longer holds what the label claims. Record how the last power cut really went and the app derives the usable capacity from your own history.
Peukert taken into account
Draw hard on a lead-acid bank and you get less out of it than a straightforward sum suggests. The estimate allows for that rather than flattering the numbers.
The power has just gone off. Backup Hours answers the only question that
matters in that moment: how many hours is the battery good for, with the
appliances you have actually got switched on?
Set up your inverter or UPS once — battery capacity in Ah, system
voltage, battery type (flooded, AGM, gel or LiFePO4) and how deeply you
are prepared to discharge it. After that you simply tick the appliances
that are running. The remaining time recalculates with every tick, so you
can see what turning off the immersion heater buys you before you turn it
off.
A Live Activity keeps the countdown on the Lock Screen, so you are not
unlocking the phone in the dark just to check.
Batteries age, and a three-year-old battery does not hold what the label
claims. Log what actually happened after an outage and the app fits your
battery's real usable capacity from your own history, rather than
trusting the figure printed on the case.
The estimate applies the Peukert relationship, so a heavy load is not
simply capacity divided by watts — drawing harder takes more out of a
lead-acid battery than the straightforward sum suggests.
Everything here is an estimate to help you plan, never a guarantee.
Battery condition, temperature and wiring all shift the real figure.
Nothing is measured by the phone, no sensor is required, and all data
stays on the device. Do not rely on this app to keep medical equipment or
any other life-critical kit running.