Generator size is not determined by home size alone. Correct sizing requires an inventory of the loads that may run together, the brief surge required to start motors, and a plan for controlling high-demand circuits.
Begin with an electrical load assessment
An installer reviews the service, panel, major appliances, heating and cooling equipment, well or septic pumps, and any special loads. Nameplate ratings and operating behavior matter more than a rough online estimate.
The goal may be true whole-home coverage or carefully managed coverage that feels whole-home in daily use. Load-management controls can temporarily delay selected equipment when demand is high.
Account for starting watts
Motors and compressors often need substantially more power for a few seconds when starting than while running. Air conditioners, heat pumps, well pumps, and refrigeration equipment are common examples. Ignoring those surges can cause voltage drop, nuisance shutdowns, or poor performance.
- List essential and optional circuits separately.
- Record voltage, running current, and starting information for major equipment.
- Consider which large loads could operate at the same time.
- Include likely future loads such as an EV charger, shop, addition, or heat pump.
Fuel and elevation affect the final design
Available fuel pressure and pipe sizing must support the selected generator. Propane systems require appropriate tank capacity and regulator design. Elevation and temperature can also reduce engine output, which is relevant across Idaho's varied climates.
Oversizing is not automatically safer: it raises purchase and fuel costs and may reduce operating efficiency. The right system balances capacity, load control, installation requirements, and future plans.