How to Read a Home Battery App: What the Numbers Really Mean
- The percentage is state of charge, not a count of hours.
- kW is how fast energy is moving, kWh is how much has moved.
- Daily import, export and self-consumption totals matter more than a single snapshot.
- A reserve setting keeps some charge back, which lowers what the battery can use day to day.
- App names and menus differ by manufacturer, so check your own manual.
Most battery apps show a flow diagram, a percentage and a few daily totals. Reading them well tells you whether the system is working as designed, and where to look if the bill does not fall.
The live flow screen
The first screen usually shows arrows between solar, battery, house and grid, each with a number in kW. These are rates, a snapshot of power right now. A battery charging at 2.5 kW does not mean it will store 2.5 kWh in a minute; it means that, if the rate held for an hour, 2.5 kWh would be added. Our explainer on kW versus kWh covers the difference.
The percentage on the battery icon is state of charge. It is a share of the usable capacity, and a battery stopping at 0% in the app is not truly empty inside: the Energy Saving Trust notes systems stop discharging at a set level, maybe 20% of capacity (Energy Saving Trust). What the app calls 0% is the manufacturer's chosen floor.
Daily and monthly totals
The history screens are more useful than the live view. Look for four numbers per day: energy imported from the grid, energy exported, energy charged into the battery and energy discharged from it. If you have solar, a self-consumption or self-sufficiency percentage is often shown too. Definitions vary between apps, so we could not give you one meaning that applies everywhere. Read the help text in your own app before comparing figures with a neighbour's.
Compare a few ordinary weeks rather than one sunny or stormy day. A single day tells you about the weather, not the system.
- Grid import in the evening should drop if the battery is doing its job.
- Battery charge and discharge should roughly follow your tariff or solar pattern.
- Export on a sunny day should happen only after the battery is full, unless you have chosen otherwise.
Modes, reserve and schedules
Most apps let you choose a mode. Names vary, but the common ideas are using the battery for self-consumption, charging at cheap times from the grid, and holding charge back for backup. A reserve setting keeps some charge for power cuts. That is sensible before a storm, but a high reserve all year leaves less for evening savings.
If your tariff is time based, check that the schedule matches the cheap window on your contract. A wrong time zone or a missed clock change is a surprisingly common cause of a battery charging at the wrong price. How the software chooses is covered in AI smart charging explained.
When the numbers look wrong
Start with the simple checks: is the app connected, is the meter or clamp reading plausibly, and has the mode changed after an update? Compare the app with your supplier's smart meter data for the same day, since the two are measured separately and can differ slightly. If the battery sits full and idle in the evening while you import from the grid, contact the installer with screenshots and dates. Reliable evidence speeds up a warranty conversation.
Common questions
Why does my battery show 100% but the house still imports power?
State of charge only says how full the battery is. If the load is higher than the inverter can supply, or the mode is set to hold charge back, the house will still draw from the grid.
Why do the app and the smart meter disagree?
They measure at different points and with different equipment, so small differences are normal. A large, repeated gap is worth raising with the installer.
Should I set a high backup reserve?
Only if outage protection matters more to you than daily savings. Raising it before a forecast storm and lowering it afterwards is a common compromise.
Related guides
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