Start with the water system and outage needs
A private well may depend on an electric pump and its controller, pressure switch, tank, treatment equipment, and any other water-system components. The generator plan should identify which parts need backup, whether they need to run together, and what the household’s water-use priorities are. Do not infer generator size from well depth or a pump’s horsepower label alone.
For households with livestock, medical or accessibility needs, or other critical water uses, state those requirements explicitly and seek appropriate professional advice. This guide does not assess water quality, sanitation, or medical needs.
Generic chart values—reference only
Champion Power Equipment’s published chart lists these ranges for common well pumps. They are generic manufacturer-published estimates, not measurements of your pump or a home-specific sizing result.
| Chart example | Running watts | Starting watts listed by the chart |
|---|---|---|
| Well pump, 1/2 HP | 750–1,000 W | 1,500–2,000 W |
| Well pump, 1 HP | 1,000–2,000 W | 2,000–4,000 W |
The source itself presents broad ranges. Do not pick a convenient value from a range or assume the value represents your pump; obtain model-specific data from the pump/control manufacturer or a qualified well professional.
Collect the exact pump and controller information
- Pump make/model, voltage, phase, horsepower, rated current, and any manufacturer-listed locked-rotor or starting-current information.
- Control-box, pressure-switch, variable-speed drive, and treatment-equipment models.
- Well-system documentation and details of any additional pumps or controls that may operate during an outage.
- Other household loads that may run at the same time, including HVAC, water heating, and refrigeration.
- The proposed generator model, fuel-specific rating, transfer equipment, and any compatible load-management controls.
If the data plate is inaccessible, have the appropriate well contractor identify the equipment. Do not open electrical enclosures or operate a pump outside its intended controls to gather information.
Pressure tank and outage plan
The pressure tank and controls affect how the water system cycles, but they do not change the pump motor’s published electrical rating. Ask the well professional whether tank condition, pressure settings, cycling, or water-treatment equipment affects the intended outage plan; do not assume a larger tank changes the generator requirement.
Prepare for an outage by keeping water-storage and conservation needs in mind, while following local public-health guidance for water safety. A generator does not guarantee that a well, pump, treatment device, or plumbing system will operate correctly.
Professional design and safe connection
Have a qualified local electrician and, where appropriate, a licensed well-system professional review the actual equipment and intended simultaneous loads. The design must address starting demand, service voltage, generator output on the selected fuel, transfer equipment, site conditions, and local permits. Request the assumptions and operating limitations in writing.
Never connect a generator to house wiring through a wall outlet. CPSC warns against backfeeding; use approved transfer equipment installed by a qualified professional. For portable generator placement, follow current CPSC guidance and the exact generator manual. Continue with the load-based sizing guide.