Battery chemistry & storage

Degradation adjusted capacity over time calculator

Enter your battery's chemistry, rated capacity, and how often you cycle it. See projected capacity at any year, plus when it drops to 80% and 70% of original.

Your numbers

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your battery
Original nameplate capacity when new.
Sets the calendar and cycle-driven degradation rates used below.
3 Your usage
Daily cycling is 7. Backup-only use is often under 1.
How far ahead you want the capacity estimate to run.
4 Advanced Optional
Overrides the chemistry default. Use a manufacturer-stated rate if you have one.

How it works

Three steps to a capacity projection

Step 1

Pick your chemistry and rated capacity

Choose the chemistry closest to your battery and enter its original nameplate capacity. If you're comparing chemistries before buying, the LFP vs NMC comparison covers the same tradeoff from the cycle-count side.

Step 2

Set your cycling frequency and time horizon

Daily solar cycling is 7 cycles a week. Enter how many years out you want the projection to run, up to 30.

Step 3

Check the result against your warranty

Compare your projected year-80% and year-70% figures against your battery's stated warranty terms with the warranty capacity guarantee calculator.

Understanding your capacity projection

How the projection combines calendar aging and cycle wear

Batteries lose capacity two ways at once: a small calendar-aging effect that happens just from sitting installed, and a larger cycle-driven effect tied to how often you charge and discharge. This calculator adds both together into a single effective annual rate, then applies it as a constant percentage loss each year, an approach consistent with how NREL's energy storage research models these two aging mechanisms as additive contributors to total capacity loss. A 10 kWh LFP battery cycled daily lands around 3.1% effective annual loss, reaching roughly 73% of original capacity by year 10.

Why cycling frequency matters as much as chemistry

Two identical batteries age at very different speeds depending on how hard they work. A battery cycled twice a day carries roughly double the cycle-driven wear of one cycled once a day, while a backup-only battery barely cycled at all degrades mostly from calendar aging, the same usage-driven divergence covered in the EV battery degradation vs home battery comparison for two very differently used battery types. The degradation vs usage pattern calculator breaks this relationship down further across different use cases.

What the 80% and 70% thresholds actually mean

Most manufacturer warranties guarantee a minimum capacity, commonly 70% to 80% of original, through a stated number of years or cycles. Once a battery drops below that range, many owners start planning for replacement even though the battery still functions, since usable runtime keeps shrinking. The end of life threshold calculator lets you set your own cutoff instead of the standard 70% or 80% marks, and the battery lifespan estimator offers an independent second projection to sanity-check the year figure this tool gives you.

What to check next

Once you know your projected capacity curve, the replacement timing tool turns that into a real calendar date, and the total cost of ownership comparison factors in what a replacement at that point would cost. This same combined calendar-and-cycle aging model factors into how the DOE's Office of Electricity projects grid-scale storage asset life for planning purposes.

Questions

Frequently asked

Most LFP batteries lose roughly 2 to 3% of capacity a year under typical daily cycling, while NMC batteries often lose 3 to 4% a year over the same use. A 10 kWh LFP battery cycled once a day typically retains about 73% of its original capacity after 10 years.

Under daily cycling, LFP typically reaches 80% capacity around year 7, NMC around year 5, and flooded or AGM lead acid around year 3. Cycling less often than daily pushes all of these dates out significantly, since less use means less cycle-driven wear.

Yes. A battery cycled twice a day degrades meaningfully faster than one cycled a few times a week, since cycle-driven wear scales with how often the battery is used, on top of a smaller calendar-aging effect that happens regardless of use. Doubling cycling frequency roughly doubles the cycle-driven portion of annual degradation.

This calculator models degradation as a constant percentage of remaining capacity lost each year, which produces a curve that fades faster in early years and slows over time. Real batteries often show a similar early pattern followed by an accelerated drop near end of life, so treat results near a battery's rated cycle life as less precise.

Related tools

Keep projecting your battery's life

Battery capacity fade projection Battery calendar aging calculator Battery end of life threshold Degradation vs usage pattern Replacement timing by chemistry Battery state of health calculator LFP vs NMC cycle life comparison All battery chemistry tools