Choosing the right generator size for your well pump is crucial. If your generator is too small, your pump won’t run efficiently—or at all. If it’s too large, you may end up overspending on an unnecessarily powerful unit. So, what size generator do you need for a well pump?
This guide will help you determine the correct generator size based on your pump’s power needs, ensuring you have a reliable backup solution during power outages.
Why Well Pumps Require The Right Generator Size
A well pump operates using an electric motor, which has two types of power needs:
Running Wattage – The power required to keep the pump running.
Starting Wattage – The extra surge of power needed to start the pump.
Many homeowners underestimate the starting wattage; which can be 3 to 5 times the normal running wattage. If your generator can’t handle this surge, your pump may fail to start or trip the generator’s circuit.
How To Calculate The Generator Size For A Well Pump
To choose the right generator, follow these steps:
Step 1: Identify Your Well Pump’s Power Requirements
Check the pump’s horsepower (HP) rating and voltage (typically 120V or 240V). You can find this information on the pump’s label or in the user manual.
Here’s a general estimate of power requirements based on pump size:
Step 2: Choose A Generator That Covers Both Running & Starting Watts
Once you know your well pump’s starting wattage, select a generator that provides at least 20% more power than required. This ensures reliable performance without straining the generator.
For example:
If you have a 1 HP pump (4000W starting wattage), choose a generator with at least 5000W capacity.
If your pump is 1.5 HP (5000W starting wattage), a 6000-7000W generator would be more suitable.
Common Generator Sizes For Well Pumps
Here are recommended generator sizes based on different well pump capacities:
1/3 HP – 1/2 HP Pumps: A 3000W to 4000W generator is sufficient.
3/4 HP – 1 HP Pumps: A 5000W to 6000W generator is recommended.
1.5 HP – 2 HP Pumps: A 7000W to 9000W generator will provide the necessary power.
If you plan to run additional appliances alongside the well pump (such as refrigerators, lights, or heating systems), opt for a larger generator to accommodate these extra power demands.
Portable vs Standby Generators: Which is Better?
When selecting a generator, consider whether a portable or standby generator is the right fit.
Portable Generators:
✅ More affordable
✅ Can be used for multiple purposes
✅ Requires manual setup during an outage
🔴 Typically runs on gasoline (requires refuelling)
🔴 Lower wattage capacity
Standby Generators:
✅ Automatically powers your well pump during an outage
✅ Higher wattage capacity
✅ Can run on propane or natural gas for longer operation
🔴 More expensive upfront
🔴 Requires professional installation
If your home relies heavily on well water, a standby generator is a more convenient and reliable long-term solution.
Additional Factors To Consider
Voltage Compatibility: Most small well pumps run on 120V, while larger pumps use 240V. Ensure your generator can handle the correct voltage.
Fuel Type: Gasoline, propane, and diesel generators each have different fuel storage and availability considerations.
Transfer Switch: A manual or automatic transfer switch allows for a safe and direct connection to your electrical system.
Final Thoughts: Choosing The Right Generator For Your Well Pump
Selecting the correct generator size for your well pump ensures you have reliable access to water during power outages. By calculating your pump’s running and starting wattage, choosing an appropriately sized generator, and considering factors like fuel type and standby options, you can keep your well water flowing without interruption.
If you need expert advice on generator installation in Prescott, Ontario, and surrounding areas, contact Beattie Dukelow Electrical Inc. We specialize in Generac Generator installations and can help you find the perfect backup power solution for your well pump and home.