What it does
Pick from 99 appliances and circuits across eight sections — Kitchen, Living Room, Bedroom, Home Office, Laundry & Utility, Garage & Outdoor, Bathroom & Personal, and Whole House. Have more than one bedroom or bathroom with gear in it? Add extra room containers, up to five of each, and every fan, lamp, and window AC in them counts toward the total. Four Florida storm presets — Hurricane kit, Window AC + fridge, CPAP + fridge + phone charging, and Pool pump + well pump + house lights — pre-tick a realistic starting list for a power cut. The verdict pane prints the steady load, the worst-case startup, and the generator size you need.
How the math works
Every checkbox adds its running watts to the total. The startup peak adds one thing only: the single biggest motor kick — a fridge compressor, a well pump, a window AC — on top of everything else already running, because only one motor can stall the generator at a moment in time and the rest are already up and turning. That peak is how real sizing guides do it. The verdict carries a 20% running-watt margin, clears the startup peak using the surge headroom actual retail generators deliver (in the ballpark of 1.25 times nameplate — a Honda EU2200i really does push 2,200 starting watts on an 1,800 running-watt machine), and then rounds up to a size you can actually buy, from 1.2 kW portable up to 26 kW standby. If the startup surge rather than the steady load is what raises your number, the verdict says so out loud.
What you leave checked matters
The picker is a strategy tool, not a wishlist. If the verdict stings, uncheck and watch: dropping the electric dryer, the pool pump, or the second window AC usually moves the number, and the page recalculates the instant you do. And bigger is not automatically better — the verdict already carries its margins, so the advice printed under it is a buy window, not a floor. A generator held under about 30% load all night carbon-fouls (mechanics call it wet slugging) and burns fuel for nothing.
Where the numbers come from
The wattage library is compiled from public, nameable sources. Refrigerator, freezer, dishwasher, and clothes-washer figures trace to ENERGY STAR performance criteria and Most Efficient lists (energystar.gov). Ceiling fans, LED lighting, dryers, and water heating trace to U.S. Department of Energy / Oak Ridge National Laboratory appliance data (energy.gov). Where a motor's spread matters, the table follows manufacturer spec data: well pumps per Goulds/Franklin motor data, pool pumps per Pentair/Jandy spec sheets, sump pumps per Wayne/Flotec spec sheets, CPAP machines per ResMed/Philips specifications, and window air conditioners derived from nameplate EER ratings. Startup surge multipliers and the retail sizing conventions come from the portable/standby generator sizing guides published by Generac and Briggs & Stratton, cross-checked against the same appliances' nameplate amps. Each entry is a typical mid-range value, not a measurement of your specific machine.
The honest framing
Gen Sizer is a planning aid, not an electrical code substitute. Real appliances vary from the table, nameplate data beats any average, and code questions — transfer switches, feeders, permits, whole-home standby hookups — belong to a licensed electrician, whose call governs any install. For anything mission-critical, put the nameplate amps × volts into the picker instead of trusting the estimate, and have the install professionally specified. Especially in Florida, where the storm season decides who needs this page.
Who made it
Gen Sizer is made by Grizzly at Kodiak Foundry LLC, a one-person studio in Florida that builds free web tools for the questions nobody hands you a manual for — you can find the rest of them, and the story behind the foundry, at kodiakfoundry.com.
Say hello
Tool requests, wattage corrections, or a storm story: hello@kodiakfoundry.com. A real person reads every message.