Will A 4000 Watt Generator Run A Well Pump?

  • By: Umer.A
  • Date: October 10, 2021
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Generally, a 4000W to 4300W generator should provide enough power to run a small well pump.

But for a bigger well pump, you will need a more significant generator with a more running wattage rating.

A standard submersible well pump with a 1 HP motor will need a 3 to 4 kW generator to start it. However, this pump will only need 1 kW as running wattage.

There are different types of well pumps, and they need other sized generators to power up. So you have to make sure that you go for the suitable generator unit for your well pump system.

How Many Watts Does It Take to Run a Water Well Pump?

First of all, you need to determine how much wattage does your well pump come with. Now there are different well pumps in terms of sizes and wattage ratings. However, they do come with their starting and running wattage ratings.

But if you don’t have a wattage rating available, you can calculate it on your own by multiplying the amperage rating and the voltage rating of your well pump.

Most well pumps that feature a 1 horsepower motor have a running wattage rating of 2000W and a starting wattage rating of 4000W. A 2 horsepower well pump has a starting wattage of 7500W and running wattage of 3750W. A well pump with a 3 horsepower motor will have a starting wattage rating of 10000W and a running wattage rating of 5000W.

What Size Generator Do Well Pumps Need?

Well pumps are pretty large, and they need plenty of power to run. They might not need a lot of wattage like an electric furnace but still need a lot of power. This is particularly due to their motor that comes in different horsepower ratings.

A well pump with a single horsepower rating will need 4000W to start and then run on 2000W. Therefore, you will need a slightly bigger generator than that otherwise, you won’t use anything else on that generator unit.

The best option for you to consider if you have a 4000W generator is to go for any other well pump with a motor under 1 horsepower. Hence, you will need a 1/3 HP well pump or 1/2 HP well pump and a 3/4 HP well pump to run with a 4000W generator.

Sizing a Generator to Your Well Pump

You must consider the sizing in your generator based on how much power is required to run your well pump. But when you use more appliances and devices, you will need more starting wattage. If your well pump has a starting wattage of 4000W, you will have to go for a bigger generator over 5000W.

To run a well pump with a 4000W generator and to be able to power other devices, you should go for a well pump that comes with a motor under 1 horsepower.

Anywhere under 1 horsepower for the motor of a well pump will work well with a 4000W generator. For example, a good option to consider is a ¾ HP motor well pump that has a starting wattage rating of 3000W and a running wattage rating of 1500W.

Is It Good to Run Your Well Pump on 4000 Watt Generators?

Yes, it’s perfectly fine to run your well pumps with your generators. There is nothing wrong there, but you should go for the right surge and running wattage rating. If the generator unit is underpowered, then it won’t be able to run your well pump. Plus, there is a risk you might end up damaging your well pump.

These 4000W generators cannot power large well pumps, and they will need more starting power and running power. So you will need a much bigger generator for that.

Can A Portable Generator Run a Submersible Well Pump?

Whether it’s a submersible water pump or any other water pump, everything is going to rely on its starting wattage rating and its running wattage rating. This rating is going to be based on the motor that it comes equipped with.

If it’s a 1 horsepower motor, the starting wattage will be 4000W, and the running wattage will be 2000W. So, to run this, you will need a portable generator that is at least 5000W. With lower horsepower, you can go for a smaller generator.

So yes, a portable generator can power a submersible well pump provided that it meets the starting and running wattage ratings of the well pump. If you can’t find the wattage rating of your well pump or you can always multiply the voltage and amperage of your unit.

Can I Plug My Well-Pump into a Generator?

Unfortunately, you can’t do that because your well pump is hardwired into your home’s electrical circuit. This is something very different from the rest of the appliances in your home.

Therefore, disconnecting these wires from your electrical panel in case of a power outage and putting them directly into a generator is going to be dangerous not only for the system but for yours as well. There is a risk of a surge, fire as well as electrocution. The best option for you is to use an extension cord for this purpose.

What size generator do I need to run a well pump and refrigerator?

To power up a well pump and a refrigerator, you will need a generator with a 5000 to 7000 wattage rating. But this entirely depends upon the starting and running wattage of your well pump and refrigerator. So you need a generator that can power them both and still have enough wattage to power something else as well.

How much does it cost to run a well pump per hour?

The average cost of running a well pump is $0.12 per kWh (kilowatt-hour). You can get a product of power consumption. Cost of electricity and operating hours to get your monthly cost. These well pumps need a lot of energy to start up.

What should be the size of the water pump?

To determine the size of a water pump, you need to look at its pressure and flow rating. In addition, you will have to determine the flow rate and pressure of the process for which you need this well pump.

A ½ HP pump can raise water from the depths up to 30 to 80 feet with water flow rates of 4 gallons per minute. And a well pump with a ½ horsepower motor will need starting wattage of 2000W and a running wattage of 1000W. This is how you determine what well pump size is required.

How often should you replace your well pump?

Based on the model and equipment type, your well pump can last around 8 to 15 years. But there are various factors at play in case of a premature expiration of your pump.

How do I calculate pump needs?

If you don’t know the wattage rating of your pump, then consult the user manual for this. If the manual also doesn’t express wattage rating, you need to note down the amperage of your well pump and its voltage. The product of these two will provide you with the relative wattage rating of your well pump.

This will be the running watts of your pump. To get the starting wattage rating, you need to multiply it by two, and you will get the starting wattage rating as well. Your generator’s wattage rating should be significantly more than this.


A 4000W generator can power up a well pump if it’s a smaller one. A well pump with a one-horsepower motor needs starting wattage of 4000W and a running wattage of 2000W. This is something your 4000W generator won’t be able to fire up.

So, you will need a bigger generator unit for this. If you are using a 4000W generator, go for a well pump with a motor smaller than a horsepower.