How Electricity Tariffs Affect Battery Payback
The value of a home battery is mostly the gap between what you pay to import electricity and what you earn to export it (feed-in). Storing solar to use at night avoids the import price but forgoes the feed-in you'd have earned — so the bigger that gap, the better a battery pays. If feed-in is close to (or above) import, storage saves little.
Why the import–feed-in gap drives payback
Every kWh you shift into the battery and use later:
- saves you the import price you would otherwise pay, but
- costs you the feed-in tariff you would otherwise have earned by exporting it.
So the net benefit per kWh is roughly import rate − feed-in rate (less round-trip losses). The calculator applies exactly this, honestly handling the case where feed-in exceeds import.
Illustrative scenarios
These are qualitative scenarios to model in the calculator with your own numbers — not sourced market rates:
| Import vs feed-in | Effect on battery value |
|---|---|
| Large gap (high import, low feed-in) | Storing solar for night use pays best. |
| Small gap | Modest benefit; payback is longer. |
| Feed-in ≥ import | Exporting can beat storing; the model may show little/no payback. |
Time-of-use tariffs
On a time-of-use plan the “import” price varies by time of day, so charging cheaply and using during peak periods can add value beyond solar shifting. Model your peak import rate in the payback calculator to see the effect.
Estimate, not a quote