How long does a home battery actually last?

If you're spending five figures on storage, you're entitled to a straight answer about how long it lasts. Here's ours, including the parts that aren't flattering.

Two numbers matter, not one

Battery warranties quote two things, and people tend to only read the first:

• The term — how many years it's covered for.
• The capacity retention — how much of the original usable capacity the manufacturer guarantees it will still hold at the end of that term.

The second number is the important one. A battery that's still "working" at year ten but only holds 60% of what it did new has quietly lost you four evenings of storage a week. The GoodWe ESA range we install carries a 10-year warranty with at least 70% capacity retention — so at the end of the warranty period, a 16kWh battery is guaranteed to still be holding at least around 11kWh.

What a cycle is, and why 6,000 of them is a long time

A cycle is one full charge and discharge. The GoodWe ESA is rated at 6,000+ cycles. Most households cycle a battery roughly once a day — fill it from the panels during the day, draw it down through the evening — so 6,000 cycles works out to somewhere north of 15 years of normal use.

That's why the warranty term and the cycle rating don't match: the cycle life typically outlasts the warranty window under ordinary household use. If you were cycling it twice a day, the maths changes.

Degradation is gradual, not a cliff

Lithium batteries don't stop one day. They fade. You'll lose a small percentage in the first year and then a slower, steady decline after that. In practice you won't notice it year to year — what you'll notice, eight or nine years in, is that the battery no longer quite gets you to sunrise in mid-winter when it used to.

That's the honest shape of it. The battery doesn't fail; it slowly does less.

Why the chemistry matters

The GoodWe ESA uses LiFePO4 (lithium iron phosphate) rather than the NMC chemistry used in a lot of consumer electronics. For a battery bolted to an Australian garage wall, that's the right trade: LiFePO4 runs cooler, is markedly more thermally stable, and delivers substantially more cycles over its life. It's a little heavier and slightly less energy-dense per kilogram — which matters in a phone or a car, and doesn't matter at all on a wall.

What actually shortens a battery's life

• Heat. This is the big one, and it's the one we control at install time. A battery in full afternoon sun on a west-facing wall will age faster than the same unit in a garage or on a shaded southern wall. Siting is not an afterthought.
• Sustained deep discharge. Regularly running a battery to empty is harder on it than cycling within a comfortable band. Good system management handles this for you.
• Chronic undersizing. A battery that's too small for the household gets worked hard every single day. Sizing it properly is a longevity decision as much as a cost one — see what size home battery do you need.

And after the warranty?

It keeps working. A battery at year eleven isn't scrap — it's a battery with reduced capacity that's now well past its payback. The modular design of the ESA range also means capacity can be added later rather than replacing the whole system, which is a genuinely different proposition from a sealed single unit.

We're not going to tell you a battery is a lifetime purchase. It's a long-life one with a known, published decline curve, which is a better thing to be able to say.

Questions about a specific system?

We install and service the GoodWe ESA range locally, sourced through AWM Echuca, so warranty claims stay in the region rather than routing through a national call centre. Call Brooke on 0408 258 298, or read our GoodWe ESA vs Tesla Powerwall 3 comparison if you're weighing the two up.