About & methodology

What GeneratorWatts is

GeneratorWatts is a free generator size calculator: you pick the appliances you want to power and it returns the exact wattage and generator size you need — no signup, no email wall, and nothing sent to a server (your selections are computed in your browser). It is published as part of vyzeapps.com.

We are brand-neutral: we are not affiliated with any generator manufacturer or retailer, and we earn nothing from the units we recommend. Picks are chosen on merit, not on who pays us — because no one does.

How we size a generator

Most calculators just sum wattages. That misses the number that actually decides whether a generator can handle your load: the starting-watt surge. Motor-driven appliances — refrigerators, well pumps, air conditioners, power tools — briefly draw 2–3× their running watts for a fraction of a second when they switch on.

Our method, applied by the calculator for your exact selection:

1. Add the running watts of everything you want powered at once.
2. Add the single largest starting-watt surgeamong those appliances — only one, because in practice motors don’t all start at the same instant.
3. Round that peak up to the nearest common generator size class for headroom.

This matches the standard industry sizing rule — total wattage equals the sum of running watts plus the highest single starting wattage — and it is why sizing on running watts alone leaves you short. You can run your own numbers with the generator size calculator.

Where our wattage numbers come from

The running and starting watts in our appliance database are industry-typical averages compiled from manufacturer power-equipment guides (Honda, Generac, Yamaha), major-retailer wattage charts such as the Lowe’s portable generator wattage chart, and U.S. Department of Energy appliance-usage data at energy.gov. Motor starting multipliers follow common National Electrical Code sizing conventions.

These are averages for planning — your specific model can differ. Always confirm the running and starting watts on your appliance’s nameplate or manual before buying a generator.

Generator safety (carbon monoxide)

Sizing is only half the job — running a generator safely matters more. A portable generator’s exhaust contains carbon monoxide (CO), an odorless gas that can kill in minutes. Following the U.S. Consumer Product Safety Commission (CPSC) and Centers for Disease Control and Prevention (CDC) guidance:

• Run generators outdoors only, at least 20 feet from the home, with the exhaust pointed away from windows, doors, and vents.
• Never run one inside a house, garage, basement, crawlspace, shed, or on a porch or carport — even with doors and windows open.
• Install battery-powered CO alarms on every level and outside sleeping areas.
• Prefer units certified to the latest PGMA G300-2023 and UL 2201-2023 standards, which add built-in CO shutoff safeguards.

Accuracy & disclaimer

GeneratorWatts provides estimates for planning purposes only, based on typical appliance wattages. Actual requirements vary by model and manufacturer. This is not professional electrical advice — always confirm against your appliance nameplates and consult a licensed electrician before purchasing or installing a generator, especially for whole-home standby systems. Questions or a correction? Email hello@vyzeapps.com.