Battery chemistry & storage
Enter your warranty's year term and guaranteed capacity. See the implied minimum for every year, and check it against your projected real degradation.
How it works
Step 1
Most warranties state a single endpoint, like 70% at year 10, which this tool converts into an implied year-by-year minimum. The warranty cycle count comparison covers the other common warranty limit worth checking alongside this one.
Step 2
This optional step projects your likely actual capacity alongside the guaranteed line, using the same model as the capacity over time calculator.
Step 3
Use this as a planning signal, then confirm with real measured data before assuming a claim is valid.
A "70% at 10 years" warranty implies a full timeline of guaranteed minimums, not just one number that matters at the very end. Assuming straight-line decline from 100% at installation, that same warranty guarantees roughly 97% at year 1 and 85% at year 5, figures that rarely appear anywhere on the product's marketing material, a gap between marketed and implied terms NREL's energy storage research has noted as a common source of consumer confusion around warranty claims. The capacity fade projection tool shows this same kind of year-by-year table for an actual degradation curve.
Warranty guarantees are almost always straight lines for simplicity, while real battery degradation compounds as a percentage of whatever capacity remains, fading faster early and slower later. That mismatch can put a battery's projected actual capacity slightly below the guaranteed line in the first year or two, even when it comfortably clears the guarantee well before the warranty ends, a gap between a flat contractual line and a curved real-world result that shows up in the EV battery degradation vs home battery comparison too.
This is a planning projection built from typical chemistry behavior, not a measurement of your specific battery. Use it to understand what a claim might look like on paper, then verify against your battery's own reported state of health using the capacity guarantee vs actual tracking tool before assuming anything about your warranty status, and cross-check the terms themselves with the warranty coverage value calculator since actual language varies by manufacturer.
If you're also concerned about hitting a cycle count limit before the year term expires, the warranty cycle count comparison covers that separate risk. Federal policy work on storage warranty standards and consumer protections is published by the DOE's Office of Electricity.
Questions
Most warranties only state a single endpoint, like 70% at year 10, but that implies a year-by-year minimum if you assume straight-line decline from 100% at installation. A 10-year, 70% guarantee implies roughly 97% guaranteed minimum at year 1, dropping evenly to 70% by year 10.
Warranty guarantees usually assume straight-line decline, while real battery degradation compounds as a percentage of remaining capacity, which fades faster in early years and slower later. This can put actual capacity slightly below the guaranteed line in year 1 or 2 even for a battery that comfortably beats the guarantee by the warranty's end year.
If a battery's actual measured capacity, verified through the manufacturer's own testing or BMS data, drops below the guaranteed minimum for that year, it may qualify for a warranty claim such as a partial credit or replacement. This calculator only projects an estimate, not verified capacity, so an actual claim requires real measurement against the manufacturer's process.
Not necessarily, since this is a projection using simplified models on both sides, not measured data. Use it as a planning signal to watch your actual capacity more closely as you approach the warranty's end year, rather than as proof of an active warranty issue.