Total kW is only the starting number
A three-phase inverter may advertise 10kW of backup output, but the useful design question is how that power can be distributed across L1, L2 and L3. Some systems allow substantial unbalance; others impose tighter per-phase limits.
List loads by phase
Before selecting backup equipment, record which circuits sit on each phase and their running and starting power. A home can have modest total demand yet overload one phase if the heat pump, induction hob or water heater are concentrated there.
Motor starts need separate attention
Pumps, compressors and workshop tools can demand several times their normal running current at startup. Compare the inverter’s short-duration backup or overload rating with the actual starting requirement rather than assuming the grid-connected AC rating applies.
Transfer architecture matters
Whole-home backup, selected-load backup and manufacturer-specific backup boxes can have different current ratings and neutral arrangements. Confirm switching hardware, earthing behaviour and local wiring rules with the exact inverter manual.
Battery power can be the bottleneck
A 10kW inverter cannot necessarily supply 10kW from the battery if the connected battery stack is limited to a lower discharge current. Pair the inverter’s backup capability with the battery’s supported power at the chosen module count.
Design for the worst credible phase
Balancing normal loads across phases is useful even when an inverter supports unbalanced backup. It reduces nuisance trips and gives more headroom for temporary peaks. See the three-phase home solar planning guide and compare exact hybrid-inverter records in the equipment catalogue.