Backup power for a well pump
Size it for the moment the pump starts, not for what it draws once it's running. A station can run a pump fine and still shut off while trying to start it.
What the pump maker says
Franklin Electric publishes minimum generator sizes for its pump drives. They're for generators, not battery stations, but they show how much extra a pump needs at start. one source so far
| Pump drive and motor size | Smallest generator Franklin lists |
|---|---|
| MonoDrive, 1/2 hp | 2,000 W |
| MonoDrive, 3/4 hp | 3,000 W |
| MonoDrive, 1 hp | 3,500 W |
| MonoDrive XT, 1.5 hp | 4,000 W |
| MonoDrive XT, 2 hp | 5,000 W |
Source: Franklin Electric SubDrive/MonoDrive manual, page 11, read Nov 5, 2026. Franklin's rule is to size the generator at 1.5 times the drive's maximum input watts. Your own pump's nameplate may say something different.
Watch the surge number
- BLUETTI Elite 300. BLUETTI lists 4,800 W, but that is a "power lifting" mode meant for heaters and similar loads. Output stays at 2,400 W, and StorageReview says it is "not a startup allowance for motors or compressors." (StorageReview)
- EcoFlow DELTA Pro. EcoFlow lists 7,200 W of surge and doesn't say for how long. (EcoFlow, its manual)
None of the makers we read list which pumps their stations can start. Email them your pump's model number and get the answer in writing.
Run your own numbers
What we haven't found yet
- Running watts and locked-rotor amps from the pump makers' own tables.
- Whether any station can start a particular pump.
Hooking anything up to a well pump's wiring is a job for a licensed electrician.