How Many Solar Panels Do I Need to Run a Well Pump?
We look at three things to determine this: the voltage the pump requires, how much power (watts) it needs at that voltage, and how much water you need per day.
The SDS-T-128 can produce about 1.5 gallons per minute, or about 500 gallons per day (6 pumping hours), at 230 feet of head on a single 150-watt, 34-volt panel. Our HR-12-328, will perform at around 10 gallons per minute, or 3,600 gallons per day, at 300 feet of head. It requires at least six 300-watt, 42-volt panels wired in two strings, giving you roughly 1,800 watts at about 120 volts.
Sizing table: watts of panel
Find your total head on the left and your gallons per day across the top. The number where they meet is the watts of panel you need at 5 peak sun hours.
| Total head (feet) | 500 gal/day | 1,000 gal/day | 1,500 gal/day | 2,500 gal/day |
|---|---|---|---|---|
| 50 | 50 | 100 | 150 | 250 |
| 100 | 100 | 200 | 250 | 450 |
| 150 | 150 | 250 | 400 | 650 |
| 200 | 200 | 350 | 500 | 850 |
| 250 | 250 | 450 | 650 | 1,050 |
| 300 | 250 | 500 | 750 | 1,250 |
| 400 | 350 | 700 | 1,000 | 1,700 |
** This is not an exact calculation table and should be used as an example only. The exact amount of power or watts will depend on your specific application.
Watts are rounded up to the next 50. If you land between two rows or two columns, use the higher one.
Two things can move that count.
Voltage. The pump controller needs a certain voltage to run, and you get there by wiring panels in a string. Sometimes the voltage calls for one more panel than the watt math does.
Cushion. A little extra panel is cheap insurance. The pump starts earlier in the morning, runs later in the evening and keeps moving water on hazy days. The controller only takes what the pump can use, so extra panel will not hurt it.
