Solar Well Pump or Windmill for Livestock Water in Arizona?
For most stock wells in this country, a solar pump is the better answer today. It reaches deeper water than a mill of the same size. It also asks for far less service through the year.
National cost guides put a solar well pump at about $2,000 to $4,000. The same guides put a windmill water pump at $4,200 to $19,600. Those are market numbers, not our price list. Solar well pump installation is work we do on ranch and stock wells, including deep ones.
A windmill still wins in one case. You have a mill that runs, a shallow well under it, and steady wind on the site. If the repair costs less than a conversion, fix the mill.
How deep will a windmill pump water, and how deep will solar go?
Depth is where the two part ways. A windmill lifts with a piston cylinder on the bottom of a sucker rod. A smaller cylinder pushes water higher but moves less per stroke.
The windmill maker Aermotor publishes a table of pumping capacities and maximum operating elevations. On the long stroke, an 8 foot wheel tops out near 216 feet of lift. That is with a 1 3/4 inch cylinder, in a 15 to 20 mph wind. It moves about 150 gallons an hour there.
Put a 3 inch cylinder on that same mill and you get about 470 gallons an hour. The lift drops to about 80 feet. Holding 150 gallons an hour at 328 feet takes a 10 foot wheel. At 491 feet it takes a 12 foot wheel on a taller tower.
Solar does not work that way. A University of Wyoming Extension bulletin says solar pumping systems can pump from depths over 1,000 feet. We have set solar pumps more than 700 feet down.
Solar well pump vs windmill: side by side
| What matters | Solar well pump | Windmill |
|---|---|---|
| How deep it lifts | Published as workable past 1,000 feet (University of Wyoming Extension) | Set by wheel and cylinder: about 216 feet on an 8 foot wheel, 491 feet on a 12 foot wheel, smallest cylinder (published mill table) |
| Water at a typical lift | 3,000 gallons a day at 120 feet of head in an extension example; 1,100 to 4,000 gallons a day in USDA-funded case studies on shallow wells | About 150 gallons an hour with a 1 3/4 inch cylinder, 470 with a 3 inch, in a 15 to 20 mph wind (published mill table) |
| Installed cost range | $2,000 to $4,000 in national cost guides; $5,188 installed in a University of Wyoming Extension example | $4,200 to $19,600 in national cost guides; the mill alone $2,000 to $13,000 before tower and installation |
| Maintenance | Reported as nearly maintenance free for years | Oil change once a year with SAE 10 non-detergent oil, plus a bolt check after a big storm |
| What fails | Controller, wiring, a stuck float switch, lightning, damage from stock and wildlife | Leathers, sucker rod, the cylinder, a dry gearbox, storm damage |
| Service life | Panel warranties reported at 20 years or more | Windmill warranties reported at five to seven years |
| What it needs on site | Sun, an open spot for the array, and a storage tank | Average wind above 7 miles an hour, and a tower |
Those ranges come from national cost guides and from USDA-funded and university extension publications. They are not a quote.
When does a windmill still make sense?
A few things have to line up. The mill has to be worth saving. The well has to be shallow enough for the wheel on the tower. And the site has to have real wind.
A USDA-funded publication puts the wind line at an average above 7 miles an hour. Below that, a mill sits parked on a lot of days while the tank drops.
Then there is the money. New leathers, a rebuilt cylinder and a length of sucker rod cost less than a whole new pumping system. If the tower is sound and the gearbox is not chewed up, repair is usually the cheaper road. Our windmill repair page covers what that work involves.
Mills have one more edge. A windmill pumps at night and through a cloudy week, as long as the wind blows.
When does solar win?
Solar wins on deep wells. A mill sized for a 400 foot setting is a big machine on a tall tower. A solar pump at that depth is an array and a submersible on wire.
Solar wins on calm ground. Canyon bottoms and sheltered draws can be dead air while the sun above them is good all year.
Solar wins where there is no power line. A USDA-funded publication says line extensions commonly cost $10,000 to $50,000 or more per mile. It says remote pumping is worth a look once you sit more than about half a mile from the grid.
Solar also wins on service calls. A mill wants a climb and an oil change every year. A solar setup usually wants a look at the controller and the float.
Is the storage tank the battery?
Yes. A solar-direct system carries no batteries. The pump runs while the sun is on the panels and fills a tank. The stock drink from that tank day and night.
New Mexico State University Extension says storage should equal 3 to 10 days of use. It says 3 days is often enough for livestock in a sunny climate. A University of Wyoming bulletin gives the same 3 day figure.
Size the tank off the herd. One extension example figured about 3,000 gallons a day for 100 cow-calf pairs in summer. Storage is the part most people undersize. Our storage tank and pipeline work is often the bigger half of a solar job.
How do you convert a windmill well to solar?
The well stays and the mill comes off the water. We pull the sucker rod, the drop pipe and the cylinder out of the casing. That leaves the hole clear for a submersible.
The solar pump goes down on new pipe and wire, set below the water level. The array goes up on a rack nearby. A controller runs the pump, and a float switch at the tank shuts it off when the tank is full.
Some owners leave the tower standing. The mill can go back on the rod later if the well and the wind ever suit it again.
Will USDA help pay for a livestock water system?
Maybe. USDA runs its conservation help through the Natural Resources Conservation Service. A University of Wyoming Extension bulletin works the NRCS Environmental Quality Incentives Program into its cost math. That math covers solar stock water.
What gets funded, and at what rate, moves by state and by year. USDA tells producers to visit the local USDA Service Center and work with staff on a conservation plan. Ask the NRCS field office for your county before you buy anything.
What should you do next?
Start with the well, not the hardware. Depth to water, what the well makes, and the run from the wellhead to the tank decide the answer.
We work wells from creek bottoms to the high country east of Globe. Ranch customers have us come through on a schedule to keep the solar setups and the mills working. Call or text (928) 961-6641 and tell us what the mill or the tank is doing. If the well itself needs work first, well pump repair is where we start.