TL;DR: Seven to fifteen years, and where you land inside that range depends almost entirely on how much power you use after dark. A 14 kWh system costs $10,000 to $18,000 installed before rebates. The arithmetic is simple; the assumptions people plug into it usually are not.
Why the Sums Changed
Two lines crossed. Retail electricity prices went up and feed-in tariffs came down, and the gap between them is what a battery monetises.
In Queensland a household might import at 25 to 30 cents per kilowatt-hour and export at 5 cents. Every unit you store and use yourself instead of selling saves the difference, 20 to 25 cents, rather than earning the 5.
In New South Wales the spread is wider still. Standard feed-in rates from the major retailers have sat around 4.9 to 7.1 cents, against peak retail rates that can exceed 40 cents. A battery shifting power across that gap is doing the same job as a 35-cent-per-kilowatt-hour subsidy.
That is the whole economic case, and it gets better every time feed-in rates fall.
What It Costs
A system with 14 kWh usable capacity generally runs $10,000 to $18,000 fully installed.
That covers the battery, the inverter if you need one, installation labour, and any switchboard work. Tesla, Sonnen, BYD and others sit across that range at different capacities and warranty terms.
What Moves the Price
Capacity. The primary driver, and the one most under your control.
Inverter. If your existing solar runs on a string inverter, adding a battery means either a separate battery inverter or replacing the existing unit with a hybrid. On systems more than about five years old, that replacement is common and it is a significant line item.
Installation complexity. Switchboard condition, cable runs, whether you want a backup circuit wired, and local labour rates.
Get three quotes from Clean Energy Council accredited installers. On the same battery in the same house, quotes routinely differ by several thousand dollars.
Rebates
The federal Cheaper Home Batteries discount cuts roughly 30% off eligible installed battery costs through the Small-scale Renewable Energy Scheme. It is applied at the point of sale by your installer and it steps down each year.
State programs stack on top in some jurisdictions. Victoria's Solar Homes Program has offered rebates up to $2,950 for eligible households. South Australia ran a Home Battery Scheme that has since closed to new applications.
These schemes are capped and they close. Check current eligibility rather than relying on a figure you read last year, and ask your installer directly whether your quote includes both federal and state support, because they do not always volunteer it.
Doing the Calculation
Total installed cost divided by annual savings.
A battery costing $12,000 after rebates and saving $1,500 a year pays back in eight years.
Working Out Your Annual Saving
The saving is what you avoid paying for grid power, not what you generate.
Estimate the kilowatt-hours you will actually pull from the battery each day, then multiply by the rate you would otherwise have paid. If you draw 8 kWh a night at 35 cents, that is $2.80 a day, or over $1,000 a year.
Two adjustments people miss.
Subtract the feed-in credits you lose. Power that used to be exported for 5 to 8 cents now goes into the battery instead, so your feed-in income falls. It is a small number against the saving, and leaving it out overstates your return.
And be realistic about how full the battery gets. A battery only earns when it is charged, and in winter, on a small array, or in a household that consumes most of its generation during the day, it will spend a lot of nights half full.
Degradation and Lifespan
Batteries lose capacity with use. Most residential warranties guarantee somewhere around 70 to 80% of original capacity after ten years or a stated number of cycles, whichever comes first.
That means your annual saving shrinks slightly over time. On a payback calculated at eight years the effect is minor; on one calculated at fourteen it is not, because the battery is delivering meaningfully less in the later years than the arithmetic assumed.
If the payback figure you are quoted is close to the warranty length, treat it as a warning rather than a result.
The Assumption to Interrogate
Ask any installer quoting a payback period which electricity rates they used.
An optimistic peak rate and a pessimistic feed-in tariff can move a payback figure by years without anything about the hardware changing. Ask for the number that produces the estimate and check it against your own bill.
Where You Land in the Range
Fast payback, closer to seven years. High evening consumption, a time-of-use tariff with a wide peak-to-off-peak spread, a poor feed-in rate, an array already producing a surplus you cannot use, and a state rebate that stacks on the federal discount.
Slow payback, past fifteen. Consumption concentrated during daylight, a legacy premium feed-in tariff, a small array, or a battery sized well beyond your evening load.
That last one is the most common and the most avoidable. Size the battery to what you draw after generation stops, not to your daily total. A household using 25 kWh a day with only 8 kWh of it after dark does not need 13 kWh of storage, and paying for capacity that never discharges is the fastest way to a bad payback figure.
Your retailer holds interval data showing exactly when you consume. Ask for it before anyone quotes you.
What the Payback Number Leaves Out
Plenty of people buy solar batteries knowing the financial case is marginal, and they are not making a mistake.
Backup power during blackouts does not appear in a payback calculation. If you work from home, keep medication refrigerated, or live at the end of a rural feeder that drops several times a winter, the value of not losing those days is real and it is not measured in cents per kilowatt-hour.
Nor is the hedge against future price rises. A battery fixes a portion of your consumption at today's cost, and retail electricity prices have moved one direction for a long time.
Be clear with yourself about which you are buying. A battery bought for resilience is a good purchase at a fifteen-year payback. A battery bought purely on financial return at a fifteen-year payback is not.
Key Takeaways
- Payback runs seven to fifteen years, driven mostly by how much power you use after dark.
- A 14 kWh system costs $10,000 to $18,000 installed, before the federal battery discount and any state rebates.
- Calculate savings from the grid power you avoid buying, then subtract the feed-in credits you stop earning.
- Size the battery to your evening consumption, not your daily total. Capacity that never discharges never pays.
- Ask which electricity rates any quoted payback figure assumes, and check them against your own bill.