Understanding your state of health result
What state of health actually tells you
State of health compares your battery's current usable capacity against what it could deliver when new, giving a direct snapshot of how much capacity has been lost so far. It doesn't tell you how fast that loss is happening or where the trend is headed, which is why one reading alone is useful but limited, and the battery lifespan estimator is a better fit if what you actually want is that longer trend rather than a single point in time.
Why the end-of-life threshold isn't a hard cutoff
A battery below its warranty's end-of-life threshold, typically 70% to 80%, can often keep running fine, just with less runtime than before. Whether that's acceptable depends entirely on your usage, since a battery that only needs to cover short outages has more flexibility than one relying on daily deep cycling, a usage-dependent tolerance the DOE's Office of Electricity also weighs when it evaluates degraded storage assets for continued grid service.
Why measurement method affects accuracy
A BMS-reported state of health can drift from true capacity over time if it isn't periodically recalibrated with a full charge-discharge cycle, so treat app-reported figures as a helpful estimate rather than a certified measurement. The premium for a longer-lived chemistry has to pay back. The levelized cost of energy calculator in our Savings & Payback section can help you test whether it does.
What to check next
If your state of health is approaching the end-of-life threshold, the replacement timing by chemistry tool and end of life threshold calculator can help you plan the next step. NREL's energy storage research covers the underlying degradation mechanisms behind these numbers in more technical depth if you want to go further.