Start with the definition on the exact datasheet
A battery may be marketed with a rounded energy figure while the technical documentation separates nominal or gross stored energy from usable energy. The usable figure is normally the better starting point for runtime calculations because it reflects the energy the system is designed to make available within its operating limits. Never assume that two batteries with similar names expose the same share of their cell capacity.
Reserve settings change what is available during an outage
Many systems let the owner preserve a backup reserve. A 10 kWh usable battery set to keep 30% in reserve does not offer the full 10 kWh for ordinary self-consumption before an outage. Conversely, the reserve is not automatically a promise that every protected load can run: inverter output power, surge capability, state of charge and the backup-panel design still matter.
Energy and power answer different questions
Capacity in kWh describes how much energy can be stored; power in kW or kVA describes how quickly the system can deliver it. A battery can have a large energy capacity but a lower continuous output than a smaller high-power system. Check continuous output, short-duration peak output and whether those ratings change when multiple modules are installed.
Account for conversion losses without inventing a single universal percentage
AC-coupled and DC-coupled systems move energy through different conversion paths. Temperature, battery state, inverter efficiency and standby consumption also affect delivered energy. Use manufacturer system data or an installer model for the exact equipment rather than applying one generic efficiency number to every product.
Use usable capacity as one input, not the whole buying decision
A sound comparison also checks chemistry, warranty throughput or cycle conditions, compatible inverter and backup equipment, operating-temperature limits, expansion rules, monitoring and service. Regional product variants can differ, so Melnti keeps exact model and source identity separate from marketing shorthand.
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