The higher your solar buy-back rate, the more income each stored solar unit gives up. Battery savings must be calculated from the spread between avoided retail imports and sacrificed exports—not the retail rate alone.
Opportunity cost changes the result
Two identical homes can receive different battery results because their retailers pay different export rates. Enter the actual rate on your current plan and rerun the calculation before switching retailer.
Peak export pricing matters
From July 2026, fair peak export pricing creates additional reasons to separate time periods. A simple daily calculator remains a conservative first screen; a full interval model should compare exporting at peaks with charging the battery.
- Check the retailer’s current buy-back terms
- Separate peak and off-peak export value
- Confirm whether battery exports qualify
- Avoid counting the same energy twice
Use the base result as a floor
If the quote only works after aggressive tariff arbitrage assumptions, label it as tariff-dependent. A robust purchase should survive a conservative solar-shifting case.