Backup Calculators

Backup power planning separates wants from needs. Critical loads—medical devices, sump pumps, communications, refrigeration—define minimum inverter and battery size. Everything else is negotiable during an outage. List critical circuits first, then add optional comforts if budget and weight allow.

UPS runtime for computers and networking gear is measured in minutes, not hours. The goal is graceful shutdown or ride-through until a generator starts. Battery capacity must cover that interval at the efficiency of the UPS inverter, including dead battery cutoff above zero percent state of charge.

Whole-home backup introduces transfer switches, generator interlocks, and load-shedding strategies. Oversizing a generator wastes fuel; undersizing prevents motor starts. Staggered start sequences and soft-start modules reduce peak demand.

Fuel storage, maintenance intervals, and exercise schedules matter for fossil generators. Battery+solar backup shifts failure modes to weather and state of charge instead of stale gasoline.

WattQuick backup calculators estimate runtime for defined loads, size UPS banks for IT gear, and help compare gasoline versus battery approaches for the same critical circuit list. Revisit the list after each outage—real events reveal surprises.