Running watts are not the whole backup-power requirement
A refrigerator, well pump, air conditioner or other motor load may run comfortably at a modest power level but demand a much larger current for a short time when starting. That transient can trip a battery inverter even when the steady-state load looks safe. Locked-rotor amps, starting current and manufacturer surge ratings are different ways of describing parts of this problem, and they must be interpreted for the exact equipment and supply voltage.
Battery and inverter limits both matter
The battery must be able to deliver the short burst of power, and the inverter must tolerate the current without exceeding its protection limits. A system advertised with a high peak rating may allow that peak only for a particular duration or under defined conditions. Do not assume that multiplying the normal running watts by a generic factor proves compatibility. Ask for the appliance nameplate and, where available, manufacturer starting data.
Load sequencing can change a backup design
Two motor loads starting at the same time can be much harder than either starting alone. Backup gateways and energy-management systems may shed or sequence loads to keep the system within limits. This is one reason a critical-loads panel can be more predictable than attempting to energize every circuit in a large home. See whole-home backup vs critical loads for the architectural trade-off.
Commission the real loads rather than relying only on paperwork
After installation, a qualified installer should test the backup transition and representative loads under controlled conditions, following the equipment instructions. Record which large loads were tested, whether they started normally and any load-control settings applied. The backup readiness checklist and commissioning record should capture that evidence. A successful test is more useful than an unsupported promise that a battery will “run the whole house.”