Generator Sizing Calculator
Size standby generators based on load analysis with A/C starting surge. Check "Manage" for loads that can be shed via smart transfer switch or load control modules.
Natural gas output is ~10% lower than LP.
Central Air Conditioning
Use nameplate LRA if available. These are typical estimates.
Why LRA matters: A/C compressors draw 5-7x their running amps during startup (Locked Rotor Amps). This surge lasts 1-3 seconds but the generator must handle it or the compressor won't start. LRA is the #1 factor that determines whether a generator is actually big enough.
Heating
+0W
+800W
+5,000W
+3,000W
Essential Loads
+200W
+200W
+1,500W
+1,500W
+500W
+100W
Large Appliances
+4,500W
+5,000W
+3,000W
+1,800W
+500W
EV Charging & Pool Equipment
+7,600W
+11,500W
+2,000W
+5,500W
+6,000W
By clicking Apply, you acknowledge that results are for reference only and must be verified by a qualified electrician against the current National Electrical Code and local amendments.
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Running Load (with 25% buffer)
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With Load Management
Generac Model Recommendation
| Model | LP Rating | NG Rating | Fit |
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For reference only. Verify all results with the current NEC and local amendments. See Terms of Use.