Solar Battery Payback Calculator Australia (2026)

Written by Jacob, Last reviewed 2026. This guide is for informational purposes only — see methodology.

Solar batteries are expensive. The example below uses an assumed installed cost of $12,000 for a 10kWh battery.

Using the assumptions below, payback can range from about 9.5 years on a strong ToU setup to about 18 years on a flat tariff.

The Battery Payback Formula

A battery pays for itself by letting you store cheap solar power during the day and use it in the evening instead of buying expensive grid power. The basic math:

Payback years = Battery cost / (Daily shifted kWh × saving per kWh × 365)

The "saving per kWh" is where things get interesting. It depends entirely on what you would have paid for that power from the grid versus what you earn by exporting it.

Worked Example: Sydney Home, Time-of-Use Tariff

Take an example Sydney household. They install a 10kWh battery for $12,000. They are on a time-of-use tariff — peak rate 50c/kWh, off-peak 15c/kWh, feed-in tariff 7c/kWh.

Every day they charge the battery from solar during the day and discharge 8kWh during the evening peak. The saving: each kWh they shift avoids 50c of peak purchases and loses 7c in FiT they would have earned from exporting it. Net saving: 43c per kWh. Over 8kWh a day, that is $3.44/day, or about $1,255/year.

Payback: $12,000 divided by $1,255 = roughly 9.5 years. That is in the ballpark where batteries start looking reasonable for households that plan to stay put for a while.

Same Battery, Flat Tariff — Big Difference

Now run the same numbers on a flat tariff. Retail rate 30c/kWh, FiT 7c/kWh. Every kWh shifted saves 30c (avoided import) minus 7c (lost export) = 23c/kWh.

Over 8kWh shifted daily: $1.84/day, about $671/year.

Payback stretches to about 18 years, so warranty terms and expected service life matter.

What Else Affects Battery Payback?

Battery cost and rebates

For this example, we assume an installed cost of $12,000 for a 10kWh battery system. Actual prices vary by installer and state. The federal Cheaper Home Batteriesprogram adds a national discount of around 30% of the upfront cost, based on usable battery capacity and eligible STCs.^[2]That can shorten payback, depending on the final installed price and annual savings.

Usable capacity and depth of discharge

Do not assume a 10kWh battery gives you 10kWh of usable energy. Use the battery's quoted usable capacity from the datasheet or installer proposal, not just the nominal capacity. Factor that into the daily shifted amount.

Cycle life and warranty

Battery warranties list the covered years, cycle limits, and retained-capacity terms. Use those figures when comparing payback with expected service life.

STCs for solar-plus-battery

Eligible batteries can receive STCs when installed with an existing, new, or replacement eligible solar PV system.^[2] From May to December 2026, the battery STC factor is 6.8 STCs per kWh of usable capacity, before any capacity tapering rules are applied.^[1]A battery installed without solar PV is not eligible for the battery STC discount.

Winter versus summer

Batteries shift less in winter because solar generation is lower and there is less surplus to store. Your annual average matters more than any single season. A battery sized for summer might sit partially empty in June and July.

Is a 10–18 Year Payback Worth It?

That depends on how long you plan to stay in the home. If you intend to be there 15 years, a battery that pays back in 10 years could leave several years of additional evening energy savings. If you might move in 5, the battery is unlikely to recoup its cost before you sell.

Some battery systems can provide backup power during blackouts if the inverter, gateway, and wiring support it. They also let you use more of your solar generation. Those benefits matter even if the pure dollar payback is marginal.

This guide is for informational purposes only. Battery payback periods are estimates and will vary based on your specific circumstances, electricity usage, tariff, and future energy prices.