Battery payback calculator
Updated 6 November 2026
Every battery size is shown side by side, so you can see where a bigger battery stops paying for itself.
How the calculator works
- Your daytime use comes out of your solar first. What's left over charges the battery.
- On a Midday Power Saver plan the battery can also charge free from the grid between 11am and 2pm (up to 24 kWh a day, shared with anything else running then).
- At night the battery runs the house first, then the car. Power for the house is worth your full usage rate; power for the car is worth only the overnight EV rate you'd otherwise pay.
- Solar-charged savings are reduced by 20% for winter. Battery losses of 10% are included. Supply charges are not changed by a battery.
- Price after rebate uses the Cheaper Home Batteries rate for May–December 2026 ($251.60/kWh first 14 kWh, 60% to 28 kWh, 15% to 50 kWh).
Prices in the calculator are typical installed prices in Melbourne. Your quote is based on your switchboard, roof and battery brand.
Questions people ask
How do I work out my daily kWh?
Your bill shows total kWh for the billing period. Divide it by the number of days. A quarterly bill of about $600 is roughly 16 kWh a day at 34c/kWh with a $1.10 daily supply charge.
Why does a 50 kWh battery pay back slower than a 13.5 kWh one?
Most homes can only fill and empty about 10–20 kWh a day, so extra capacity sits unused. On top of that the federal rebate drops to 60% above 14 kWh and 15% above 28 kWh.
Can I charge a battery without solar panels?
Yes. On a Midday Power Saver plan in Victoria the battery can charge from the grid free between 11am and 2pm, then run the house in the evening. Check that your battery and inverter can charge from the grid on a schedule.