Battery chemistry & storage
Enter the capacity you need and your planning horizon. Compare five chemistries on the factors that matter for occasional backup power, not daily cycling.
How it works
Step 1
Light, infrequent cycling changes which factors matter most. If your actual use looks more like daily cycling, switch to the best chemistry for daily cycling comparison, since it ranks the same chemistries differently.
Step 2
The horizon determines how much calendar aging matters relative to the upfront price difference between chemistries.
Step 3
A cheaper chemistry upfront may retain less capacity by the time you actually need it. The calendar aging calculator can help you dig deeper into any single chemistry's projected curve.
Light cycling means cycle life almost never becomes the limiting factor, so the tradeoffs that matter for daily use, like cost per year driven by cycle count, largely disappear from the picture. What replaces them is calendar aging and self-discharge, both of which matter more for a battery that mostly sits idle waiting for an outage. Before comparing chemistries, it's worth confirming the capacity itself with the whole home backup sizing calculator, since backup-only sizing follows different rules than a daily-cycling system.
Lead acid's short cycle life is a serious liability for daily use but barely matters for occasional backup power, since the battery may never come close to its cycle limit over a normal planning horizon. That leaves its low upfront cost as a genuine advantage rather than something offset by frequent replacement, unlike the picture in the daily cycling comparison, a cost-versus-resilience tradeoff the DOE's Office of Electricity also weighs when evaluating backup storage investments.
A battery cycled daily gets recharged constantly as a side effect of normal use, but a backup-only battery can sit for weeks or months between real events, giving self-discharge time to meaningfully reduce available charge. A chemistry with higher self-discharge may need a periodic top-off to stay ready, worth checking directly in the self discharge rate calculator. Chemistry and inverter have to agree. The hybrid inverter sizing calculator in our Inverters & Equipment section can help you size the inverter for the battery you have picked.
If you're deciding between LFP and lead acid specifically for a backup application, the lithium vs lead acid comparison covers that head-to-head in more depth. NREL's energy storage research covers the broader resilience and backup-power storage picture if you want to go deeper on the underlying science.
Questions
For pure backup power with light cycling, lead acid's low upfront cost becomes far more competitive than it is for daily cycling, since cycle life rarely becomes the limiting factor. LFP still wins on calendar aging and self-discharge, so the right choice depends on whether upfront budget or long-term capacity retention matters more for your situation.
A battery cycled once a month instead of once a day takes roughly 30 times longer to use up the same number of cycles, so even lead acid's much shorter cycle life rating can stretch across many years of infrequent use. Calendar aging and self-discharge become the more relevant wear factors instead.
Yes, more than it does for a daily-cycling system, since a backup battery spends most of its life idle rather than being regularly recharged by routine use. A chemistry with higher self-discharge may need periodic top-off charging to stay ready for an actual outage.
It depends on your time horizon and budget. LFP's better calendar aging means it retains more capacity over a long period of light use, which matters if you want the battery ready for a worst-case outage many years from now, while lead acid's lower upfront cost may be the more practical choice for a shorter planning horizon.