Our generator wattage calculator takes the guesswork out of sizing your setup. Every generator listing throws numbers at you: peak watts, running watts, surge watts. The real question is simpler: will it actually run what you need? This calculator does the math for you. Pick a scenario below or check off the specific gear you’re powering, and we’ll tell you exactly how many watts you need and which generator in our lineup covers it — whether that’s a weekend of tent camping or backup power for the whole house.
Table of Contents
For a full breakdown of our top picks, see Best Camping Generators for 2026, or browse the complete generators lineup.
Quick start: pick a scenario
Your generator needs
Running Watts vs. Starting Watts (and Why It Trips People Up)
Most undersized-generator problems come down to one mistake: sizing only for running watts. Running watts (also called rated or continuous watts) are what an appliance draws once it’s already on. Starting watts, sometimes called surge or peak watts, are the extra jolt a motor-driven appliance pulls for a second or two when it first kicks on — a refrigerator compressor, a sump pump, an RV air conditioner. That surge can be two to four times the running wattage.
The good news: you don’t need to add up every appliance’s starting watts separately. In practice, appliances rarely all start at the exact same instant, so the standard sizing method — the same one generator manufacturers use in their own charts — is to add up everyone’s running watts, then add just the single largest surge on top. That’s exactly what this calculator does.
How We Built This Generator Wattage Calculator
The appliance wattage figures come from published generator sizing charts (Champion Power Equipment’s wattage chart and similar manufacturer references), cross-checked against multiple sources. They’re representative values meant for planning, not a substitute for your specific appliance’s nameplate rating. If precision matters — you’re right on the edge between two generators — check the label on the appliance itself (usually on the back or bottom) for its actual watts, or its amps, which you can multiply by voltage (120V for most household and RV circuits) to get watts.
Generator specs (running/rated watts, peak/starting watts, noise level, weight) are pulled from each manufacturer’s official spec sheet or product listing for the exact model we carry.
Frequently Asked Questions
How many watts do I need to run a 13,500 BTU RV air conditioner?
Roughly 1,700 running watts, with a surge up to about 3,200 watts when the compressor kicks on. That puts it out of reach of a basic 2,200-watt inverter generator on its own — you’ll want at least a 3,000-running-watt unit, like the Champion 4000W Dual Fuel or the Westinghouse iGen5000, especially if you’re also running a fridge or lights at the same time.
Can one generator run my whole house?
Only a whole-home standby generator (typically 20,000+ watts) can run every circuit in a house at once. A portable generator can cover your essentials — refrigerator, sump pump, some lighting, maybe a window AC — but not central air, an electric water heater, and a well pump simultaneously. Use the calculator’s Home & Whole-House tab to see exactly where your list lands.
What’s the difference between peak, starting, and surge watts?
They generally mean the same thing, just labeled differently by different manufacturers: the momentary extra power a motor-driven appliance pulls for a second or two when it first turns on, before settling down to its running wattage. On a generator’s own spec sheet, “peak watts” usually refers to the maximum surge the generator can briefly supply — not a wattage it can sustain continuously.
Do these wattage figures apply exactly to my appliance?
They’re representative figures from manufacturer wattage charts, useful for planning purposes. Your specific appliance can vary by brand and age — check its nameplate for the actual running watts or amps if you’re sizing right at the edge between two generators. This generator wattage calculator uses those same manufacturer figures.
Bookmark this generator wattage calculator for next time. Ready to shop? See our full Best Camping Generators for 2026 breakdown, or browse the complete generators lineup.