Running a water pump off-grid sounds ideal, but miscalculating solar panel needs leads to wasted money and unreliable water supply. Here’s how to size it right.
To run a 0.75 HP solar water pump efficiently, you’ll typically need 4 to 6 solar panels of 250W each, depending on sun hours and system efficiency.
Don’t stop here—let’s break down why sizing is critical for solar pumping systems.
How many solar panels do I need to run a water pump?
The number of solar panels required depends on the pump’s horsepower (HP), voltage, and the average sunlight in your location. For a 0.75HP solar water pump:
Power Consumption: A 0.75HP pump equals about 560 watts (1 HP = 746 watts, adjusted for efficiency ~75%).
System Losses: Factor in 30% loss (inverter, wiring)
Calculation Example:
560W ÷ 0.7 (loss adjustment) = 800W needed.
So, you need at least 2pcs of 400W or 550W to cover the load reliably.
How many solar panels are required for a 7.5HP submersible pump?
A 7.5HP powered water pump is much larger and demands robust solar infrastructure.
Power Consumption: 7.5HP = ~5.6kW.
System Losses: Add 30% margin for inverter and other inefficiencies.
Calculation Example:
5.6kW ÷ 0.7 = 8.0kW needed.
This means you require about 15 x 550W solar panels (8.25kW total). In regions with lower sunlight, 18 panels may be safer.
Additionally, a 7.5HP submersible pump will require a larger inverter and possibly a battery bank for continuous operation.
What size inverter do I need to run a 0.75 borehole pump?
For a 0.75HP borehole pump, inverter sizing must match both the running and starting power demands.
Running Power: 0.75HP = ~560W.
Starting Surge: Submersible and borehole pumps often require 2–3x surge power. Surge = 1.5kW – 2kW.
Inverter Size Recommendation:
Continuous Power: At least 0.75kW inverter.
Surge Power: 2kW minimum surge capacity.
Also consider voltage matching (DC voltage from solar panels vs. AC pump motor voltage). If using batteries, ensure the inverter supports your battery bank voltage (e.g., 24V or 48V systems).
Summary
Size your solar system right—2 panels for 0.75HP pumps,15+ for 7.5HP pumps. Match inverter to surge demands.
