How Much Solar Power is Required to Run a Well Pump

Understanding the amount of solar power necessary to power a well pump is crucial for those looking to generate their own energy while ensuring their water supply is reliable and sustainable. This guide will walk through the necessary calculations to determine the right solar setup for a well pump, based on various factors.

Understanding Your Well Pump Requirements

Firstly, it's essential to know the specific details of the well pump you are planning to run. Factors such as the depth of the well, the flow rate required, and the type of pump (such as submersible or jet pump) play significant roles.

Calculating the Power Requirement

Assuming a well with a 100-foot depth and a flow rate of 10 gallons per minute, a 1 horsepower (hp) pump would generally suffice. However, to account for additional requirements, such as a landscape watering system, a 1.5 hp pump is recommended.

To begin, we need to convert horsepower to watts:

1.5 hp × 746 watts/hp 1119 watts. Dividing by efficiency (assuming 80%), we get: 1119 watts ÷ 80 efficiency 1400 watts.

Given a 120-volt system, the current required by the motor is calculated as follows:

1400 watts ÷ 120 volts 11.7 amps.

This calculation assumes an efficiency of 0.8. Depending on the actual efficiency, this number might vary.

Panel Size and Battery Requirement

To ensure the pump can run effectively under all conditions, a detailed analysis of the power requirements is necessary. Here are the key considerations:

1. Start-Up Current: When starting, the pump's locked rotor amps (LRA) can be as high as 70 amps. This means a battery is essential to provide the necessary power during the start-up phase. For a 50 amp-hour battery, it may suffice, but it depends on starts per hour, which can vary based on usage and weather conditions.

2. Higher Capacity Battery: To be more conservative and ensure reliability, a 100 amp-hour battery is recommended. However, to charge this battery in a single sunny day with 5 hours of sunlight, the panels must produce 20 amps per hour, which translates to 2800 watts of panels or more than 10 panels.

Conclusion

As you can see, the calculations involved in determining the right solar power setup for a well pump are complex and depend on various factors, including pump requirements and efficiency. It's crucial to use accurate data and calculations to tailor the system to your specific needs, ensuring reliable operation and conservation of resources.

Key Points:

The power requirement for a 100-foot well and 10 gallons per minute with a 1.5 hp pump is approximately 1400 watts. An 80% efficiency factor is applied to ensure reliability. A 100 amp-hour battery is recommended for higher reliability and to handle start-up currents. Solar panel requirements vary based on daily weather conditions and usage patterns.

By carefully considering these factors, you can effectively harness solar energy to power your well pump, ensuring a reliable and sustainable water supply.