What Size Generator to Run a Well Pump: Hourly Cost Analysis

If you rely on a well for your household water supply, then asking what size generator to run a well pump is not only essential but also a mandatory question. In recent years, states like Texas have faced extended power outages, which leaves the residents without access to water. Whether you are building a new home or improving an existing one, learning about a backup power solution for your well pump is considered a practical decision.

Most homeowners usually rely on fuel-powered generators to keep their well pumps operational. However, as the diesel cost rises and sustainability has become a priority, most Americans have started to turn towards solar-powered generators, like Jackery Solar Generator. These portable solar-powered generators offer reliable solar backup solutions, which ensure that you get uninterrupted water access during prolonged power outages.

Key Takeaways

• Since well pumps have high surge wattage, choosing a generator 20–30% larger than the pump’s peak power ensures smooth operation without overloads.
• A 2,500 - 5,500-watt generator is sufficient for a 1 HP submersible pump, depending on the wattage of the well pump and supports additional household appliances like a refrigerator and lights.
• A 1/2 HP pump needs at least a 1,000 - 3,000W generator, while a 2 HP pump requires a 3,000 - 7,500W generator to handle starting and running wattage effectively.
• Jackery Solar Generator 5000 Plus can power well pumps efficiently, eliminating fuel costs and providing a sustainable off-grid solution.

How Many Watts Does a Well Pump Use?

Under normal conditions, an average-sized well pump operates at 700 - 800W. However, larger well pumps, like deep well submersible pumps, can even consume between 2000 - 5,000W during starting before stabilizing at their running wattage.

Let’s assume that your well pump runs for 8 hours a day, then the total energy consumption can be calculated using the simple formula where you multiply the total wattage by the number of hours. In this way:

• Daily Usage: 700W x 8 hours = 5.6kWh
• Monthly Usage: 5.6 kWh x 30 days = 168kWh

How Many Starting & Running Watts Does a Well Pump Use?

The starting and running watts of a well pump depend on its size. For example, if you are wondering what size generator is needed for a 1/2 HP well pump, you first need to understand its power requirements. A 1/2 HP well pump typically requires 1,500–3,000 watts of surge power at startup before stabilizing at 900 watts during continuous operation. Similarly, some of the users on Reddit have reported that their well pump surges up to 2,500W before settling at 700-800W for continuous operation. 

When selecting a diesel, inverter, or even solar generator for a well pump, it is crucial to understand the difference between starting watts and running watts. Like most motor-driven appliances, well pumps demand a high initial power surge to start the motor.

Here’s a comparison table description of how many watts a well pump uses:

Note: The above data is curated from the internet and wattage may vary as per the brand, efficiency, and demographic.

How Much Energy is Needed to Run a Well Pump?

The energy needed to run a well pump depends on multiple factors. Suppose you are using a jet pump that consumes 800W and is operational for 6 hours per day. Then, it would require 4.8 kW/day or 144 kWh/month.

At the same time, you will always need to consider efficiency losses of up to 15% that happen with almost all generators and electrical systems. These losses occur due to heat dissipating, voltage fluctuations, and other inefficiencies. In such cases, we need to have an extra 10-15% energy buffer. So, the same 800W jet pump would now require 5.52 kW/day or 165.6 kWh/month.

As you can see from the above example, when determining the energy requirement to run a well pump, you will need to consider different factors, like the pump’s power rating, daily usage duration, and efficiency losses that naturally occur in any electrical system. When you account for these parameters, you will ensure you finalize the right generator size to keep your well pump running efficiently.

Types of Generators Suitable for Well Pumps

When you ask what size generator to run a well pump, you should also consider asking which type of generator is ideal for a well pump. Selecting the right generator is not only about matching wattage requirements; it also involves considerations about power reliability, fuel efficiency, long-term cost, and operational convenience.

Given a well pump’s reliance on a high-wattage, motor-driven system, this household appliance requires a generator that can handle surge power demands, provide stable electricity output, and even ensure long-term efficiency during extended power outages. Moreover, a well-sized generator should handle the well pump's starting and running wattage without overload. Additionally, fuel efficiency and cost play a crucial role, as running a generator for an extended period can lead to significant fuel expenses.

Before finalizing what size generator to run a well pump, you need to compare different generator types. The following table chart will help you understand the ideal generator for your well pump and other household needs.

Apart from these pros and cons, another important factor that you need to consider is the gasoline cost that will impact your overall utility bill. According to a report published by EIA, the average price of diesel in February 2025 was $3.148 per gallon. The rising cost of diesel further emphasizes the need to choose a generator that balances fuel consumption with performance.

What Size Generator to Run a Well Pump?

Wondering what size generator to run a well pump? You need to understand that choosing the right generator size for a well pump is a little tricky because, unlike standard household appliances, it requires both running and surge wattage. The key to selecting the right generator size for a well pump is to calculate its power requirements and then account for the initial power surge and any other electrical loads.

To simplify this process, check out the following steps using a real-world example of a 3/4  HP well pump.

Step 1: Find the Running Wattage

The running wattage is the amount of continuous power a well pump would need once it has started. A 3/4 HP well pump would have a 550 - 800W. Since most well pumps operate at either 120V or 240V, with higher voltage pumps consuming fewer amps and 1 HP is equivalent to 746W:

Watts = Horsepower x 746 = 0.75HP x 746W = 560W (approximately)

Step 2: Determine the Surge Wattage

Like air conditioners, well pumps also experience a temporary surge in power demand when they start. The surge wattage is often 2-3 times the running wattage, which again depends on the type of the pump. For the ongoing example of a 3/4 HP well pump, the estimated surge wattage is:

Running Wattage = 560W

Surge Wattage = 560W x 2.5 = 1,400W

This means that if you want to run a 3/4 HP well pump, your generator should have a rated output of at least 560W and a surge peak output of more than 1,400W.

Step 3: Add a Safety Buffer

Apart from surge wattage, you should also consider adding a safety buffer when answering what size generator to run a well pump because a well pump’s power demand fluctuates based on water depth, pipe pressure, and a few environmental factors. To be safer, it is recommended to include a safety margin of 1.25 times above the surge wattage.

So, for the 3/4 HP well pump that needed a generator of at least 560W:

With Safety Buffer = 560W x 1.25 = 700W

Step 4: Account for Additional Loads

Let's just assume that a well pump is not going to be the only household appliance that you intend to run with your generator. There are several important appliances, like refrigerator, air conditioner, television, CPAP machine, etc., that one uses during power outages. So, when calculating the size of the generator required for a well pump, it is also considered a healthy practice to account for other loads.

Let’s assume you intend to power a refrigerator (800W) and portable fan (200W) alongside your well pump with your generator, then:

Total Power = 700W + 800W + 200W = 1700W

So, it means that the generator should be upgraded to at least 1700W rated output to handle a 3/4 HP well pump alongside multiple household appliances at home.

How to Calculate Cost Per Hour Use of Well Pump?

After you have learned what size generator to run a well pump, another important factor that you need to consider is the cost of using the generator for running the well pump. By evaluating the exact cost of using a generator for a well pump, you will be able to make a well-informed decision.

In order to calculate the cost of using a generator, you will need to include the well pump’s wattage, efficiency of the generator, overall duration of operation, and current diesel price. For this calculation, let’s consider the cost of diesel to be $3.68 per gallon and a ½ load diesel generator of 10kWh consumes 0.53 gal/hr.

Here’s an estimated breakdown of the cost that you need to pay for generators when used for different well pumps:

*The on-grid cost is taken from EIA.

Based on this table, using a 2 HP well pump with a diesel generator for eight hours will cost you $4.64. Assuming that you intend to run this well pump for 8 hours daily for a full 30-day month, the cost would be $139.20.

So, if you rely entirely on a diesel generator to power your well pump for 8 hours per day, you would end up spending around $139.20 per month just on fuel costs. Over a year, this adds up to nearly $1,700, which makes diesel generators an expensive long-term solution compared to solar-powered alternatives.

Best Jackery Solar Generators for Well Pumps

Jackery has a line of solar generators, portable power stations, and solar panels that are effective when it comes to powering different well pumps. The solar-powered generators from Jackery are compact in design, feature a large battery capacity, and are ideal for powering well pumps alongside different household appliances.

If you don’t want to pay nearly $1,700 each year just for diesel charges for your diesel generator and wish to move to a more reliable, eco-friendly, and solar generator for well pumps, then you can check out the following Jackery Solar Generators. These portable units are idle for those who want a backup power solution for extended power outages or for outdoor living.

Jackery Solar Generator 5000 Plus

The Jackery Solar Generator 5000 Plus is a versatile power solution that is designed to meet substantial energy needs, which makes it an ideal solar-powered generator for operating well pumps and other high-wattage appliances, like washing machine, sump pump, water heater, etc. The Jackery Solar Generator 5000 Plus’ substantial continuous output ensures it can manage the high surge and running wattages required by well pumps, including those with higher horsepower ratings.

Appliance Running Hours

• Deep Well Submersible Pump (1000W) = 4.0H
• Centrifugal Pump (1200W) = 3.4H 
• Jet Pump (900W) = 4.5H 
• Shallow Well Pump (800W) = 5.0H
• Gear Pump (700W) = 5.7H 
• Diaphragm Pump (400W) = 9.5H

Customer Review

“I've tested it with high-demand devices, and it [Jackery Solar Generator 5000 Plus] powered them without issues for up to 15 hours.” -- Kendra.

Jackery Solar Generator 2000 Plus

The Jackery Solar Generator 2000 Plus provides a high-capacity battery and robust power output, which makes it well-suited for running various types of well pumps, including those with higher horsepower ratings. Jackery Solar Generator 2000 Plus offers a dependable and flexible power source for operating well pumps and other small-to-mid-sized household and outdoor appliances.

Appliance Working Hours

• Deep Well Submersible Pump (1000W) = 1.6H
• Centrifugal Pump (1200W) = 1.4H 
• Jet Pump (900W) = 1.8H 
• Shallow Well Pump (800W) = 2.1H
• Gear Pump (700W) = 2.3H 
• Diaphragm Pump (400W) = 4.0H

Customer Review

“Everything works great! Very satisfied with the entire package; it will do exactly what I need it to, and I highly recommend this unit to everyone. Super easy to use and maneuver.” -- John.

FAQs on What Size Generator to Run a Well Pump

What size generator do I need to run a 1 HP well pump?

A 1 HP well pump typically requires 1,500 watts of running power but experiences a power surge of 3,750 watts during startup. To ensure smooth operation without overloading the generator, you should select a generator with a minimum capacity of 4,000–4,500 watts.

Can a 5500-watt generator run a well pump?

Yes, a 5,500-watt generator can easily power most well pumps, including a 1 HP submersible pump. Since a 1 HP well pump requires around 1,500 running watts and surges up to 3,750 watts, a 5,500-watt generator provides enough overhead to handle this demand.

How many watts do I need to run my well pump?

The wattage required to run a well pump depends on its horsepower (HP) and whether it is a shallow or deep well pump. A typical well pump, a 1 HP well pump, will have 1,500 running watts and 3,750 surge watts. For such well pumps, you would require a minimum of 4,000W generator.

What size generator is required to run a 1 HP submersible pump?

A 1 HP submersible well pump requires approximately 1,500 running watts but needs 3,750 watts of surge power when it starts. To ensure stable operation, you should choose a generator with at least 4,000–4,500 watts of capacity. If you need to run other appliances alongside the well pump, a 5,500–6,000-watt generator is a better choice.

Can a Portable Generator Run a Submersible Well Pump?

Yes, a portable generator can run a submersible well pump, but it must be properly sized to handle the pump’s starting and running wattage. Since submersible well pumps require a high surge wattage during startup, you must select a generator that exceeds the pump’s peak power demand. For example, a 1 HP submersible pump requires around 3,750W at startup, meaning a 4,500–5,000W portable generator is recommended.

Conclusion

When you start evaluating your monthly utility charges, it is highly advisable to account for the amount of energy a well pump consumes, especially if you rely on a generator as a backup power source. If you keep on wondering what size generator to run a well pump, then you will also need to consider the cost of the same. Traditional fuel-powered generators can be expensive to operate in the long run, and if you wish to ensure uninterrupted access to water and have long-term sustainability, then you can always check out Jackery Solar Generators that offer clean, quiet, cost-effective alternatives, which eliminate your fuel dependency and even reduce overall monthly expenses.