How many solar panels to run a well pump?
About 2 panels at 400 watts under national-average sun, working from 1.5 kWh a day. The count runs from 1 in desert sun to 2 in the cloudiest states. That answers the energy question; the timing question (this load at night, panels at noon) is the part most listicles skip, so it gets its own section below.
Panels by sun figure
400W panels, 0.77 derate, count rounded up; the right column shows what the rounded-up count actually produces against the load's 1.5 kWh day.
| Peak sun hours | Panels | Daily margin |
|---|---|---|
| 4.0 h | 2 | ~2.5 kWh vs 1.5 needed |
| 4.5 h (US avg) | 2 | ~2.8 kWh vs 1.5 needed |
| 5.0 h | 1 | ~1.5 kWh vs 1.5 needed |
| 5.5 h | 1 | ~1.7 kWh vs 1.5 needed |
| 6.0 h | 1 | ~1.8 kWh vs 1.5 needed |
| 6.5 h | 1 | ~2 kWh vs 1.5 needed |
Where the 1.5 kWh figure comes from. A 1/2 HP submersible pump draws about 1,000W running, but household water use only runs it 1 to 2 hours a day: call it 1.5 kWh. Deeper wells with 1 HP-plus pumps scale up proportionally.
The part after the panel count
Two panels of daily energy, and the smallest energy figure on this site next to the freezer. But the well pump is the classic trap load for off-grid builds, because its problem was never energy: a 1,000W pump wants 2,000 to 3,000W for the second it starts, and it starts whenever the pressure tank says so, including 2 a.m. So the true off-grid bill of materials is modest panels, a battery, and an inverter sized for triple the running watts, or a soft-start kit, or a larger pressure tank to make starts rarer. Energy is cheap here; surge is the spec that costs money.
For outage backup specifically, the pressure tank buys grace: a typical tank holds several flushes and a kettle after the power drops. Households that just want water security often skip solar entirely and fit a larger tank plus a generator inlet; the panel math on this page is for the ones going properly off-grid.
Questions people ask
How many solar panels does it take to run a well pump?
About 2 400-watt panels at the national-average 4.5 peak sun hours, from a planning figure of 1.5 kWh a day. Strong desert sun brings it to 1; cloudy states need 2. Those counts cover daily energy; running the load at night takes a battery or a grid connection, covered below.
What surge does a well pump need from an inverter?
Plan on 2 to 3 times running watts for a split-second: a 1,000W half-horse pump wants a 3,000W-surge inverter to start reliably, and marginal inverters brown out right at the pressure switch. Soft-start kits tame the spike where inverter budget is tight.
Does this count include a battery?
No. The table answers the energy question: how many panels produce what the load consumes over a day. Grid-tied homes need nothing else; the grid absorbs the timing. Off-grid, add storage for the dark hours (the page discusses sizing for this load) and an inverter rated for the start-up surge where the load has one.