Generator Sizing Guide: What Size Generator Do I Need? | PES Supply
Generator Sizing Guide: What Size Generator Do I Need?
Complete guide to sizing portable, standby, and inverter generators for any application
How to Size a Generator
To properly size a generator, calculate the total wattage of all devices you want to run simultaneously, then add 20% for safety margin and motor starting surge.
Quick Sizing Reference
| Generator Size | Running Watts | What It Can Power |
|---|---|---|
| 2,000W | 2,000W | Refrigerator, lights, phone charger, TV |
| 3,500W | 3,500W | Refrigerator, lights, TV, microwave, small AC |
| 5,000W | 5,000W | Essential household + window AC, water pump |
| 7,500W | 7,500W | Most household essentials + central AC (small) |
| 10,000W | 10,000W | Full household backup (small-medium home) |
| 15,000W | 15,000W | Large home, central AC, well pump, electric dryer |
| 22,000W | 22,000W | Whole home backup (large home, all circuits) |
| 26,000W+ | 26,000W+ | Large estate, multiple AC units, workshop |
Appliance Wattage Reference
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator | 700W | 2,200W |
| Central AC (3-ton) | 3,500W | 10,500W |
| Window AC (10,000 BTU) | 1,200W | 3,600W |
| Water Heater | 4,000W | 4,000W |
| Well Pump (1/2 HP) | 1,000W | 3,000W |
| Microwave | 1,000W | 1,000W |
| Electric Range | 3,000W | 3,000W |
| Clothes Dryer | 5,400W | 6,750W |
| Sump Pump (1/2 HP) | 1,050W | 3,150W |
| LED Lights (10) | 100W | 100W |
Generator Types Compared
| Type | Cost Range | Fuel Type | Noise Level | Best For |
|---|---|---|---|---|
| Portable | $500-$3,000 | Gas/Propane | 65-75 dB | Job sites, camping, occasional use |
| Inverter | $400-$4,000 | Gas | 50-60 dB | Tailgating, RVs, electronics |
| Standby | $3,000-$15,000 | Nat Gas/Propane | 60-70 dB | Whole-home backup, automatic start |
| PTO | $1,000-$3,000 | Tractor | Varies | Farms, large properties |