Skip to content
Standby Generator Guide

THE HOMEOWNER’S PLANNING DESK

Whole House Generator Sizing Calculator & Load Planner

Build a whole house generator load plan from your equipment inputs and compare essential, unmanaged and managed scenarios before an installer assessment.

Planning estimate

By Standby Generator Guide Editorial Team · Published October 5, 2026 · Updated October 6, 2026 · Method and source checks October 5, 2026

Planning estimate — confirm final sizing with a qualified installer using equipment nameplates and manufacturer requirements. Tools prepare questions and scenarios; they do not approve an electrical or fuel-system design.

Technical professional review pending.How this guide is reviewed

Prepared by our editorial research desk using linked sources. No licensed professional signoff or hands-on testing is claimed. See the review process and what remains to be reviewed.

Mode A — Quick guided planning

Choose the loads you want backed up. Nothing is selected for you. This creates an editable worksheet, not an approved generator size.

Choose your home’s equipment

Which equipment belongs in your plan?

Check only the specific equipment you want backed up. Well and sump references apply only to the displayed horsepower. The range entry covers one burner, not a complete cooking appliance.

References use the upper end of Champion Power Equipment, Generator Wattage Chart, checked 2026-10-04. They are published planning references, not measurements of your household. Unlisted equipment receives blank watts, never zero. Medical loads need a separate continuity plan; generator startup does not provide uninterrupted power.

Mode B — Advanced / verified inputs

Want to see how the planner works?

Load an illustrative example, then replace every value with the actual nameplate or manufacturer data for your home. Examples use the upper end of ranges from Champion Power Equipment, Generator Wattage Chart; they are not household defaults or generator recommendations.

Enter equipment/nameplate data or values confirmed by your installer. No invented appliance defaults. “Total starting watts” includes that load’s running watts; for no extra starting demand, enter the same value in both fields. Do not convert motor LRA directly to watts. Volts and amps are documentation fields and do not automatically calculate watts; power factor and motor-start behavior must be verified.

The default 20% is an adjustable editorial scenario, not a code requirement or a validated sizing factor.

How the load-planning scenarios differ

All loads

Sum running watts × quantity

Add largest extra starting contribution

Essential only

Remove optional loads

Recalculate the largest extra start

Managed illustration

Keep unmanaged loads

Allow one managed row at a time

Editorial model. Different motors starting together, starting kVA, voltage dip and site derating still require a qualified assessment.

Read the result as a discussion range

Running load sums every selected unit. Starting contribution is the largest extra starting demand of one load row, with all units in that row assumed to start together. Planning load = running load + that contribution. Several different motors starting together can need more. Power factor, starting kVA, voltage dip, phase balance, altitude and temperature are not modeled.

The essential-only scenario excludes optional loads. The managed scenario keeps all unmanaged loads running and allows only one managed row at a time. Priority labels help document your preferences; they do not simulate an installed controller. A checkbox cannot make an unmanaged appliance controllable.

Medical equipment may require uninterrupted power and a separate continuity plan. A standby generator has a transfer interruption. Discuss the equipment requirements with its provider. View the separate sourced appliance reference chart or understand ATS and load management.

Save is optional. Saved plans stay in this browser’s local storage and are not sent to us. Shared devices can expose saved entries. Avoid names, addresses, medical details and other personal information. Clearing saved data does not delete an exported PDF.