Sizing & buying
What size standby generator do I need?
Start with what you actually want powered. Square footage alone is not enough because air conditioners, pumps and other motors can have large startup demands.
What do you want powered?
Select the major loads you want available during an outage. This is an educational estimate, not a substitute for a professional load calculation.
Selected steady-load estimate: about 3.0 kW before starting surges and design margin.
The important distinction
Essential-load backup
Keeps selected necessities operating—often heating controls, refrigeration, pumps, lighting and selected outlets. This can reduce generator size and project cost.
Whole-home coverage
Aims to support much broader household use. The actual design still depends on simultaneous loads and whether smart load-management equipment is used.
Why a professional calculation still matters
Starting loads
Compressors and motors can need substantially more power for a short period when they start.
Fuel derating
Available output can differ by fuel and model, so the nameplate kW is not the only number that matters.
Load management
Some systems can temporarily shed selected large loads, letting a smaller generator handle more of the home intelligently.