How long does a home battery last? 8–15 years — but cycles aren't the number that matters.

Most quality home batteries sold in Australia use lithium iron phosphate (LFP) chemistry, are rated for roughly 6,000 to 10,000 charge cycles, and typically deliver 8 to 15 years of service when cycled about once a day. The more meaningful measure is capacity retention rather than cycles: the mainstream Australian warranty guarantees at least 70% of original usable capacity after 10 years, with some brands offering 70% and some 80%. That figure is a floor for warranty claims rather than a prediction, so a well-treated battery often sits above it at year ten, and reaching the end of the warranty does not mean the battery stops working — it continues at gradually reduced capacity. A battery is generally considered end of life below roughly 60 to 70% of original capacity. The sensible planning assumption is a 10 to 15 year asset that stores slightly less each year.

Tesla warrants the Powerwall on a time basis over 10 years with a capacity retention guarantee, and unlike some competitors it does not impose a cycle limit for normal residential use, which is one of the reasons it is often treated as the benchmark. Expected service life is broadly the same as other quality lithium home batteries: think of it as a 10 to 15 year asset that gradually stores less. As with any brand, the warranty threshold is a floor for claims rather than a forecast of where capacity will land, and the unit will typically keep working beyond the warranty period at reduced capacity. Read the actual warranty document rather than a summary, since the terms differ by product generation and by market, and check whether the retention figure is quoted against usable or nominal capacity. It is also worth confirming who performs warranty service in your area and what the typical response time is.

Between 2016 and 2022 the Canberra Battery Test Centre ran independent accelerated cycling trials on 26 home battery models, and only 2 of the 26 completed the full test program without a major fault or failure. Most units suffered early faults, control or communication failures, or significant capacity loss ahead of expectations. A Pylontech LFP module was estimated to retain approximately 70% capacity at ten years and was one of the two to finish without major problems. Two caveats matter when reading this. The tested models were from the 2016 to 2022 generation and battery technology has genuinely improved since, particularly the shift to more thermally stable LFP chemistry, and accelerated cycling is harsher than normal domestic use. But the central lesson holds: most failures were not cells wearing out, they were electronics, control boards, communications and firmware. That is why local support and installation quality matter more than headline cycle figures.

Four factors, two of which you can influence. Heat is the biggest accelerator of capacity fade, which makes installation placement critical: a battery on an unshaded western wall or in a hot roof space will age noticeably faster than the same unit in a cool, ventilated garage, and that decision is made once and lives for a decade. Depth of discharge is the second, since routinely running a battery to empty and back to full stresses cells more than shallower cycling, and a battery undersized for your load or aggressively cycled by a virtual power plant works harder every day. Calendar ageing is unavoidable, costing roughly 0.7% of capacity a year purely from the passage of time regardless of use, which is why an oversized battery you rarely cycle is not automatically longer lived. The fourth factor is the quality of the electronics and installation, which independent testing suggests causes more real-world failures than cell wear does.

Yes. Lithium iron phosphate batteries characteristically lose a small amount of capacity relatively quickly in the first months of use, then settle into a long, slow, much flatter decline. A drop of around 3 to 5% in the first year is within normal expectations and is not the beginning of a steep slide. What should prompt attention is a different pattern: a sudden step change in capacity, a decline that keeps accelerating rather than flattening, or capacity falling well below the trajectory implied by the warranty. Those suggest a fault rather than ordinary ageing, and they are worth raising with your installer and the manufacturer while the warranty is still active rather than waiting. Keep your own records — note the usable capacity your monitoring reports in the first month and again each year, because a documented trend is far more persuasive in a warranty conversation than a recollection that it used to last longer.

Nothing sudden. A battery is generally considered end of life below roughly 60 to 70% of original capacity, which in practice means it no longer carries your evening the way it once did and you start drawing from the grid earlier than you used to. It does not stop working. You have several options and none of them is urgent: keep using it, since a battery at 65% capacity is still saving you money; reduce what you ask of it by shifting heavy loads such as hot water, EV charging or the pool pump into your solar window instead; add modules if you have a modular stackable system, subject to the manufacturer's rules about mixing new and aged modules; or replace it, at which point prices, rebates and tariffs will look very different from today, noting that the current federal battery scheme is legislated to end in 2030. When it does come out, home batteries are recyclable and there is a growing Australian recovery industry.