Generator sizing calculator
Tick everything you'd want running at the same time during an outage. The calculator adds up the running watts, then adds the single largest starting surge (motors rarely all start in the same instant), then adds 20% headroom so the generator isn't working flat-out. The method is explained in the sizing guide.
The wattages below are typical estimates for planning. Your appliances' nameplate or manual figures always take precedence — motor loads especially vary by model and condition.
Your result
Tick at least one appliance above to see a recommendation.
- Total running watts: 0 W
- Largest single starting surge: 0 W extra
- Peak demand (running + largest surge): 0 W
Recommended size (with 20% headroom): 0 running watts
Your selection includes a 240 V appliance — you need a generator with 120/240 V output, regardless of wattage.
That's small-generator territory. Start here:
- Small generators under 2,500 W
- Inverter generators (quiet, clean power)
- Best for a refrigerator and essentials
A mid-size portable covers this — up to 7,200 W fits through a 30 A inlet:
You're above the 30 A ceiling — look at large portables with a 50 A connection:
At this size a permanently installed standby generator is the realistic path:
How the math works
- Running sum: every ticked appliance's running watts, added together — the load the generator must sustain continuously.
- One surge, not all: only the largest single (starting − running) difference is added, because compressor and pump starts are momentary and staggered. If you know two big motors will genuinely start simultaneously, size up.
- 20% headroom: generators running at their limit run hot, loud, and thirsty — and dual-fuel units make fewer watts on propane or natural gas than their gasoline rating. Headroom absorbs both.
These typical wattages are planning estimates, not measurements of your home. For hardwired circuits (furnace, well pump, water heater) a transfer switch or interlock installed by an electrician is required — see the guide.
EV charging and electric water heating are unusually large discretionary outage loads. Before including them, read how generator-powered EV charging works and compare the electrical requirements of 120 V and 240 V heat-pump water heaters. Shedding either load can move a home into a much smaller generator class.