Power determines simultaneous load
kW measures the rate of power delivery or use. Check continuous inverter output, overload duration, per-phase limits and motor starting. A large battery does not necessarily start a large pump: power and energy are separate requirements.
Capacity describes available energy
kWh measures energy. For illustration, a 1 kW average load over 4 hours uses 4 kWh at the load. Battery selection also accounts for usable capacity, conversion losses, reserves, temperature and end-of-life condition. This simple calculation is not a procurement specification.
Storage does not automatically mean backup
Grid-connected systems may shut down on grid loss. Continued supply requires isolation, a local voltage/frequency reference, backup circuits and verification of islanded PV operation. Define protected loads, transfer behaviour and duration.
What does a UPS do?
UPS addresses power quality and continuity for designated loads; storage commonly supports energy management and backup, while generators serve longer outages. They can coordinate, but capacity alone does not make them interchangeable. Critical sites need qualified whole-system assessment.
Further reading & references
Tesla · How Powerwall worksSchneider Electric · Healthcare energy resilienceReferences explain general principles, not brand partnerships, compatibility or project certification. Site-specific design and local requirements apply.