About GeneratorMath
GeneratorMath exists because generator sizing advice on the internet is mostly written by people selling generators. Brand blogs size you into their product line; forum answers skip the surge math; and the one number that decides everything for pump owners — 240V capability — routinely goes unmentioned. We built the version we wanted: 29 appliance calculators and 6 outage scenarios across 6 categories, each one showing its formula, its watt ranges, and where those numbers come from.
We recommend a size class, not a product
Unlike generator-brand blogs, the output of every calculator here is a size class — "3,500–4,500W portable", "14–22kW standby" — never a specific model. Size classes are stable market conventions; specific recommendations age badly and invite bias. The site carries clearly-marked affiliate links (which search the recommended class, not a chosen product), and the math is computed before and regardless of any link: quantities come from sourced constants whether or not you ever buy anything.
What makes this site different
- Surge-aware math, stated openly. Running watts add; starting surges don't — only the largest single surge counts, assuming staggered starts. Every page states this assumption instead of hiding it. See the methodology.
- Ranges, not fake precision. Appliance wattages genuinely vary, so we publish min–max ranges with named sources and compute on typical values — and every page tells you to check your nameplate.
- Honest pages stay honest. The electric water heater and EV charger pages exist mostly to tell you those loads usually don't belong on portable generators. A site selling generators can't say that; we can.
- Safety is content, not a footer link. Every calculator page carries the same four rules — CO placement, no backfeeding, electrician-installed transfer switches, proper cords — because generator deaths are placement deaths.
- No sign-up walls. Every calculator is free and works instantly.
Who maintains it
The site is maintained by GeneratorMath Editorial Team. The wattage dataset was last reviewed on; each calculator page shows the same date so you always know how fresh the numbers are. Corrections are the fastest way to make the site better — if a manufacturer publishes different figures or you spot an error, emailhello@generatormath.com and we will fix it and credit the correction.
How the site makes money
GeneratorMath may earn from clearly-disclosed affiliate links (marked "affiliate link" wherever they appear — see the full disclosure) and from display advertising. Neither affects the math: watt figures, surge deltas and class recommendations are computed from the sourced dataset regardless of what, or whether, you buy.
Start with the multi-appliance builder, browse thefull calculator index, or readhow the sizing math works.