Home Battery Warranties Explained: Cycles, Throughput, Degradation
Short answer: Compare cycles, throughput, and guaranteed capacity together. Years alone tell you almost nothing — a warranty can end on a throughput limit long before its calendar years run out.
Planning estimate only — not a quote, not tax advice, not installation advice. Get a site-specific quote from a licensed installer, check your utility's rules, and speak to a tax professional before buying.
This is where two batteries that look identical on a quote stop looking identical. Brands measure “life” differently, and the difference is buried in the warranty wording. This post explains the terms so you can compare like with like. It does not publish cycle counts or warranty years for any brand, because no brand-specific warranty figures were in the research reports for this build — check the manufacturer's spec sheet for the exact product you are quoted.
| Term | What it means | What to ask / compare |
|---|---|---|
| Cycles | One full charge-discharge cycle (partial cycles usually count proportionally, per the spec sheet) | How cycles are counted, and what capacity is guaranteed after that many cycles |
| Throughput | Total energy (kWh) the battery is warranted to deliver over its life | Throughput limit vs cycle limit — which one ends the warranty first for your use? |
| Degradation / capacity retention | How much usable capacity remains after years or cycles | Guaranteed capacity % at year X, and how it is measured |
| Years | Calendar warranty length | Years vs cycles vs throughput — the warranty usually ends at whichever limit is reached first |
The side-by-side sheet to demand
- Get the spec sheet for each exact model quoted — not a general brand page.
- Write down, side by side: cycles, throughput, guaranteed capacity %, years, and exclusions (temperature, depth of discharge, installer requirements).
- Ask: does daily cycling for bill-shifting use up the warranty faster than backup-only use? Get the answer in writing from the installer/manufacturer.
- Ask: who handles a warranty claim — installer, manufacturer, or both — and what labour is covered?
TODO: Add a brand comparison table only after spec sheets for the exact models quoted in the comparison are checked and dated. Do not copy warranty figures from a blog or directory.
Frequently asked questions
Is a longer warranty always better?
Not if it is measured differently. Compare cycles, throughput, and guaranteed capacity together — a 10-year warranty with a low throughput limit may end sooner for a daily-cycling home than a shorter warranty with a higher throughput limit.
Does using a battery every day void the warranty?
It depends on the spec sheet's cycle/throughput limits. Ask the manufacturer/installer in writing how daily bill-shifting affects warranty coverage for your use pattern.
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