Watt~calc

Home Battery Payback Calculator Australia 2026

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Work out the real payback of a home battery in Australia, with the May 2026 federal Cheaper Home Batteries rebate netted off automatically. Enter your usable capacity, installed price, retail and feed-in rates, and how much solar you currently export — the calculator returns net cost, year-1 savings, payback period and 15-year lifetime benefit.

Battery and household

Most popular sizes: 10, 13.5 (Powerwall 3), 16 kWh.
Total quoted price, before federal rebate.
Check your bill or solar app — the energy currently sold at feed-in tariff.
300 = average solar household. 365 = aggressive daily cycling.
Typical Australian default offer: 28–35 c/kWh in 2025–26.
Most retailers now pay 4–7 c/kWh for exported solar.
Modern LFP batteries deliver ~88–92% after losses.
2%/yr is typical for LFP across a 15-year life.
Tiered: ~$258/kWh first 14 kWh, ~$155/kWh 14–28 kWh, ~$39/kWh 28–50 kWh.
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Your battery payback

Payback period
—
to fully recover net cost
Year-1 savings
—
retail offset minus lost feed-in
Federal rebate
—
May 2026 program
Net out-of-pocket
—
price after rebate
Net at 10 years
—
cumulative savings minus net cost
Lifetime net (15 yrs)
—
total benefit over battery life
Net cumulative position (savings minus net cost)
Year-by-year savings table
Year Energy delivered Annual savings Cumulative savings Net position

How to use this calculator

  • Enter the battery's usable capacity, not nameplate. A 13.5 kWh Powerwall 3 has ~13.5 kWh usable; some brands quote nameplate ~10% higher than usable.
  • Use the installed price your installer quoted, before any rebates. The calculator nets off the federal rebate automatically.
  • Daily solar surplus matters more than capacity. If you only export 6 kWh/day, a 16 kWh battery is mostly wasted — model the smallest battery that fits your surplus first.
  • Use your retailer's current rates. The wider the gap between retail and feed-in, the faster the battery pays back.
  • Set cycles realistically — 300/yr is typical; 365 only applies if you fully discharge every single day, which most households don't.

Key assumptions

  • Federal rebate tiers: ~$258/kWh for first 14 kWh, ~$155/kWh for 14–28 kWh, ~$39/kWh for 28–50 kWh, capped at 50 kWh (May 2026 round, indicative).
  • Daily charge is the lower of: your stated solar surplus, or capacity × cycles ÷ 365.
  • Each kWh delivered is valued at (retail rate − feed-in tariff), since that's the kWh you would otherwise have exported at the feed-in rate.
  • Capacity degrades each year by the rate you set (2%/yr by default — broadly in line with major LFP warranties).
  • Retail rates and feed-in tariffs stay constant across the 15-year projection. If retail rises faster than feed-in, the result is conservative.
  • 15-year battery life. Some products are warranted to 10 years; others to 15. Adjust expectations accordingly.

Frequently asked questions

How much is the May 2026 federal rebate worth?
It's tiered by usable capacity: roughly $258/kWh for the first 14 kWh, $155/kWh for the 14–28 kWh band, and $39/kWh for 28–50 kWh, capped at 50 kWh per household. A 13.5 kWh battery ≈ $3,500. A 27 kWh stack ≈ $5,600. The calculator does this maths for you.
How does a battery save money in plain terms?
It stores solar that would otherwise be exported at the feed-in tariff (~5 c/kWh) and lets you use it later instead of buying grid power at the retail rate (~32 c/kWh). The net saving per kWh is the gap — about 27 c/kWh in this example, or $0.27 for every kWh the battery cycles through.
Why does my daily solar surplus matter more than capacity?
You can't store what you don't have. If you only export 6 kWh/day, a 16 kWh battery sits half-empty most days. The smartest battery is sized to your typical evening + overnight load, capped by what your panels actually export.
Should I oversize solar before adding a battery?
Often yes. A bigger solar system creates the surplus that makes a battery worthwhile. If your roof allows, model solar payback first (try our solar payback calculator), then layer a right-sized battery on top.
Does this account for VPP revenue?
No. Some virtual power plant (VPP) programs pay extra during demand events but require you to give up control of the battery at peak times. If you plan to join a VPP, ask the operator for an annual revenue estimate and add it to the savings line manually.
What happens after 15 years?
Most LFP batteries are warranted to retain ~70% of original capacity at 10–15 years. After that, they keep working at reduced capacity until cell-level failure, often well past year 15. The calculator stops at 15 years to keep projections realistic.

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This calculator provides general estimates only and is not financial, energy or product advice. Federal rebate values are indicative and may change — always confirm the current program rates and your eligibility with an accredited installer before purchasing. Never sign a contract with a non-CEC-accredited installer.