Is my home battery paying off? How to check

A battery saves money by storing cheap energy, usually your own spare solar, and using it later instead of buying power from the grid at a higher price. The saving shows up as smaller bills, but bills also move with the seasons, price changes and how much you use, so one bill before and one after can mislead you.

Three ways to measure the saving

1. Compare bills from the same season. Put a winter bill from before the battery next to a winter bill after it, and compare the cost per day rather than the total, because bill periods differ in length.
2. Use your battery's own data. Your inverter app shows how much energy the battery supplied each day. Each of those kWh saved roughly your usage price, minus the feed-in credit you gave up by storing the solar instead of exporting it.
3. Price your meter data. Your retailer or distributor can give you half-hourly smart meter data. Pricing it against your plan shows exactly what you paid and when, which also tells you whether a different plan would suit your battery better.

Why savings can fall short of the quote

• The backup reserve is set high, so a large share of the battery is never used day to day.
• Your electricity plan doesn't reward the battery. If your evening price is low, each kWh the battery supplies saves less.
• The battery is bigger than your evening and overnight use, so it rarely empties.
• There's little spare solar in winter to fill it.
• A virtual power plant (VPP) is using stored energy that your home would otherwise have used.
• The battery has a fault or has gone offline, which is easy to miss if nobody is watching the numbers.

What to do next

Start with your battery's settings: ask your installer what the reserve and operating mode are and why. Then check whether your plan still suits a home with a battery. Battery Coach does both checks from your own data and keeps watching each month.