Solar Water Pump Calculator
Size solar panels for irrigation pumps, livestock watering, and water transfer. Enter flow rate and head pressure — get pump watts and panel count.
Check this if you need the pump to run after dark. Adds battery sizing to the calculation.
How to Use This Calculator
Enter your flow rate
The flow rate in GPH (gallons per hour) is how much water your pump needs to move. For livestock, estimate 2-3 gallons per head per hour. For drip irrigation, add up the flow of all emitters. Convert GPM to GPH by multiplying by 60.
Set head pressure
Head pressure in feet is the total resistance the pump must overcome — vertical lift plus friction in pipes. A shallow well at 40 feet depth = ~40 ft of head. Add 1 foot of head per 10 feet of horizontal pipe run for friction losses. Most solar pump systems operate between 20 and 200 feet of total head.
Pump run hours
Enter how many hours per day the pump needs to run. Continuous circulation systems run 24 hours. Irrigation systems typically run 6-10 hours during the day. Livestock watering runs on demand, typically 4-8 hours.
Nighttime pumping option
If you check nighttime pumping, the calculator adds battery storage to cover evening and night operation. Without a battery, solar pumps can only run during daylight. For storage tank systems, you can pump all day and store water, avoiding the need for batteries.
The Formula
The constant 0.1885 converts GPM and feet of head to hydraulic watts. Pump efficiency accounts for motor and impeller losses — a 60% efficient pump requires 1.67× more electrical power than the theoretical hydraulic minimum. Solar panel sizing uses a 20% derate for real-world conditions (temperature, angle, partial shading).
Example: Livestock Watering System
Ranch with 100 head of cattle
A cattle ranch needs to pump 1,500 GPH from a 60-foot deep well for 6 hours daily to fill a storage tank. They want daytime-only pumping (no battery).
Result
The 3-panel, 1,200W solar array powers the pump directly during daylight hours. Water fills a storage tank during the day, providing a continuous supply for livestock without any battery storage.