Two batteries can both say “10 kWh” and behave very differently
Energy capacity answers how much energy a battery can store. Power capacity answers how quickly that energy can be delivered. The U.S. Department of Energy makes the same distinction at grid scale: storage is characterized by both energy capacity and power capacity. For a home, that difference determines whether a battery can simply run lights and electronics or also support heavier loads.
The battery numbers that change real-world use
| Check | Why it matters |
|---|---|
| Nominal vs usable kWh | Reserve limits and depth-of-discharge rules can make usable energy lower than the label |
| Continuous discharge power | Sets the sustained load the battery can support |
| Peak / surge limits | Relevant to motors, pumps, compressors and short-duration high loads |
| Battery voltage | Must match the inverter architecture |
| BMS communication | Closed-loop communication can improve charge control and state-of-charge reporting |
| Parallel limits | Determines how far the bank can be expanded later |
| Cycle-life test conditions | Cycle claims are not meaningful without DoD, temperature and end-of-life conditions |
| Warranty throughput / retention | A “10-year warranty” may include energy-throughput limits and capacity-retention conditions |
Why LiFePO4 is common in stationary storage
Lithium iron phosphate (LiFePO4/LFP) is widely used in stationary battery products. Buyers should still compare the complete battery system rather than chemistry alone: cell quality, BMS design, current limits, enclosure, thermal management, certifications, warranty support and inverter compatibility can matter as much as the chemistry label.
Runtime is a load problem, not a battery-label problem
A rough runtime estimate starts with usable energy divided by average load, with an allowance for conversion losses. A 10 kWh nominal battery operated to 90% usable depth and through a 92% efficient conversion path would not deliver the entire 10 kWh to AC loads. Use the battery runtime calculator to make those assumptions explicit.
Do not assume a 48 V battery and a 48 V inverter are automatically a supported pair. Check the manufacturer’s current compatibility list, required firmware and communication protocol.
Warranty questions worth reading before checkout
- How many years are covered?
- Is there an energy-throughput or cycle limit?
- What capacity retention is guaranteed at the end of the period?
- What operating-temperature and installation conditions can void coverage?
- Is labor or shipping included in a claim?
- Who provides support in your country?