Solar for well pumps

Most Colorado homes run a submersible pump between 1/2 and 1-1/2 horsepower on a 240-volt circuit. A 1/2-hp pump draws roughly 1 kW while running; a 1-hp pump roughly 1.5–2 kW; a 1-1/2-hp deep-well pump in the foothills can draw 2–2.5 kW. The pump’s data plate or the well log lists horsepower and full-load amps, and amps times 240 gives running watts closely enough for planning.

The number that trips people up is startup surge. A submersible motor draws two to three times its running current for a fraction of a second when it starts, and some deeper pumps more. A 1-hp pump that runs at 1.8 kW may momentarily demand 4–6 kW. A generator or battery inverter that cannot supply that surge simply trips, and the pump never starts. This is why a small portable power station will not run a well, and why the inverter’s motor-start rating matters more than its kilowatt-hour capacity.

Daily energy is small once the pump is running. A household pump cycles perhaps one to two hours a day in total, which is 1–3 kWh — a fraction of a 13.5 kWh battery. The battery’s job is to be big enough in watts to start the motor, not big enough in kilowatt-hours to run it.

The Tesla Powerwall 3 is rated for 11.5 kW of continuous output with a motor-start capability well above what a 1-hp submersible needs, so a single unit starts and runs the pump with the furnace blower, fridge, and lights alongside it. SigEnergy’s SigenStor and Enphase’s IQ Battery system publish their own continuous and peak ratings; for a 1-1/2-hp or deeper pump we check the pump’s locked-rotor amps against the inverter datasheet before quoting, because that is the pass-fail number.

The pump also has to be on the backed-up side of the house. We usually wire a backup-loads panel that carries the well pump, pressure switch, furnace or boiler controls, refrigerator, freezer, internet, and a few lighting circuits. Whole-home backup is possible with a larger battery stack and is the right call for homes with electric heat or a second pump. Either way, when Xcel or a co-op de-energizes the line, the battery islands the house automatically and the pump keeps working.

Outages on rural Colorado feeders last longer than in the metro area: long lines, wind, wet snow on trees, and wildfire safety shutoffs that Xcel has used in December 2025 and again in 2026. Co-op territory has its own realities, with crews covering large service areas. A day-long outage is ordinary in the foothills and on the plains; multi-day outages happen most winters somewhere in the state.

Your pressure tank is a small amount of stored water — typically a few gallons to a few dozen gallons of drawdown depending on tank size — and it is the only water you have once power is lost without a battery. A larger pressure tank or a cistern with a small pump extends that, and some owners add a cistern for wildfire defense as well. But a battery that starts the well pump is what turns an outage from a water emergency into an inconvenience.

Solar makes the battery last. A 6–10 kW array on a clear Colorado day refills a 13.5 kWh battery by early afternoon even in winter, so a multi-day outage does not drain you on day one. Snow on the panels is the exception; the snow-on-panels page covers what to expect.

For a well home, we size the solar array to annual usage as usual — well pumps add perhaps 500–1,000 kWh a year, which is one or two more panels. The battery sizing is driven by the pump’s surge and by what else you want covered. One Powerwall 3 (13.5 kWh, roughly $19,000 for the first unit installed) handles a 1-hp pump plus essential loads for a day or more; a second unit (roughly $12,000) buys whole-home backup or a second night without sun. SigenStor starts at 9 kWh (about $15,500) and grows in 9 kWh modules.

As of September 2026, Colorado exempts residential batteries from state sales tax and offers a 10% state income-tax credit on battery purchases for tax years through 2026 — that deadline is close, so a battery finished this year is worth more than the same battery next year. The federal 30% homeowner credit ended for systems placed in service after 2025. The blackout-runtime calculator shows how many days a given battery and array combination keeps the pump and essentials running.

A DC solar well pump is a different animal: a low-voltage submersible or surface pump wired directly to a few panels through a controller, with no battery and no grid. It pumps when the sun shines and stops when it doesn’t, filling a stock tank or cistern that acts as the storage. Ranchers across eastern Colorado and the Western Slope use them for pastures miles from a power line, where a utility extension would cost more than the pump.

Complete kits with pump, controller, and panels run roughly $1,500–$6,000 depending on depth and flow, and prices vary widely; deep wells or high flow rates cost more. We do not sell or install these. The right source is a well driller or an agricultural pump supplier who can match the pump curve to your static water level and daily gallons. If the site has grid power and a barn or shop, that is where we come in with a ground mount or roof array and, if needed, a battery.