What will a generator run
Two numbers tell you what a portable generator runs: running watts handle everything at once, and starting watts get the largest motor going.
Sizes of generators
| Size | Loads it runs alone | Starting watts | Gasoline an hour, half load |
|---|---|---|---|
| 2,000 watt generator | 19 of 25 | 2,500 W | 0.25 gal, $1.07 |
| 3,000 watt generator | 21 of 25 | 3,750 W | 0.31 gal, $1.32 |
| 3,500 watt generator | 22 of 25 | 4,375 W | 0.35 gal, $1.49 |
| 4,000 watt generator | 22 of 25 | 5,000 W | 0.38 gal, $1.62 |
| 5,000 watt generator | 23 of 25 | 6,250 W | 0.45 gal, $1.92 |
| 6,500 watt generator | 24 of 25 | 8,125 W | 0.55 gal, $2.35 |
| 7,500 watt generator | 24 of 25 | 9,375 W | 0.62 gal, $2.65 |
| 8,000 watt generator | 25 of 25 | 10,000 W | 0.65 gal, $2.77 |
| 10,000 watt generator | 25 of 25 | 12,500 W | 0.79 gal, $3.37 |
| 12,000 watt generator | 25 of 25 | 15,000 W | 0.92 gal, $3.93 |
| 13,000 watt generator | 25 of 25 | 16,250 W | 0.99 gal, $4.23 |
| 15,000 watt generator | 25 of 25 | 18,750 W | 1.12 gal, $4.78 |
For a typical portable, starting watts reach 125% of the power rating used while running; your model's label shows its own figure. On each size's page, you'll find the 25 loads listed one by one.
Running loads together
| Running together | Running | Peak at a start | Smallest portable | Its starting watts |
|---|---|---|---|---|
| Fridge, freezer, lights, TV, router | 1,470 W | 2,270 W | 2,000 W | 2,500 W |
| Fridge, 1/2 hp sump pump, lights | 1,600 W | 2,700 W | 3,000 W | 3,750 W |
| Fridge, 1 hp well pump, lights | 2,550 W | 4,550 W | 4,000 W | 5,000 W |
| Fridge, 1 hp well pump, microwave, lights | 3,750 W | 5,750 W | 5,000 W | 6,250 W |
| Fridge, window AC 10,000 BTU, lights, TV | 2,150 W | 3,350 W | 3,000 W | 3,750 W |
| Freezer, fridge, 1 hp well pump, window AC, lights | 4,250 W | 6,250 W | 6,500 W | 8,125 W |
The smallest portable's running load stays within 80% of its rating, and its starting watts cover the peak. Lights refers to 10 LED bulbs. Each load's running and starting watts appear in the appliance wattage chart.
How starting watts make the choice
Two to three times its running watts are needed to start a motor, and this surge lasts a second. A 1 hp well pump uses 2,000 W to run and 4,000 W to start. A 3,500 W generator handles it while running, but stalls when it kicks on. Generators of this type give about 25% beyond their running rating during that second.
Begin with the biggest motor, then add the small loads. To power a whole house with a standby unit, use the size calculator.