What size generator do I need?
Tell us what you want the generator to power. We’ll handle the wattage math underneath.
Why this size
How SizeDial calculated this
SizeDial adds the running watts of all selected loads, then adds the largest additional startup surge from any one selected motor-driven load. This follows the common generator-sizing worksheet method used by major generator manufacturers. Actual appliance labels override estimates.
Logic version: generator@1.1.0
Size for what runs together, then leave room for the biggest startup surge.
Running watts are the continuous demand. Starting watts are the brief extra demand when a motor or compressor starts. Honda and Generac both distinguish these two numbers when estimating generator size.
Do not rely on generic appliance estimates when the label is available
Preset values are useful for planning, but real equipment varies. Check the appliance data plate or manual, especially for pumps, air conditioners, furnaces, refrigerators, and power tools.
240-volt loads change the generator you need
Enough wattage is not enough if the generator does not provide the voltage and receptacle configuration your equipment requires. SizeDial flags selected 240-volt loads so you remember to verify that before buying.
Ready to shop the size you calculated?
Calculate your size above to get a more specific shopping link.
Generator sizing FAQ
Why not just add all starting watts?
Most startup surges do not occur at exactly the same instant. A common sizing method is total running watts plus the largest additional starting requirement. If your use case intentionally starts multiple large motors together, size more conservatively.
Is this a whole-house standby-generator design?
No. It is a shopping estimator for portable or backup generator capacity. Permanent standby systems, transfer switches, fuel supply, and electrical installation should be sized and installed appropriately.
Primary method source: Honda Power Equipment generator wattage estimation guide, verified September 8, 2026. Preset values are estimates; appliance nameplates override them.