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A deep well is where cheap solar pumps give up. The little kits you see for under $200 are built for shallow water a few dozen feet down. Pull water from 200, 400, or 800 feet and you need a real submersible built for the lift. This guide walks through how to size a solar deep well pump correctly, so you buy once, using the Grundfos pumps we carry at Krato Power.
Everything about sizing a deep well pump comes down to total head and daily flow.
Total head is how far the pump has to push water up, measured from the water level in the well (not the drilled depth) to where the water comes out, plus a bit extra for pressure and pipe friction. The key figure is where the water actually sits, called the standing or pumping water level. A 500-foot well with water standing at 200 feet is a 200-foot lift problem, not a 500-foot one.
Daily flow is how many gallons you use per day. Size the pump so it can move that volume during the hours the sun is strong, then store it in a tank. On solar, you design around the day's total, not instant demand.
Get those two numbers and the pump almost picks itself.
Depth capability is set by the pump, not by solar in general. Across the Grundfos line we carry:
The pattern holds everywhere in pumping: the deeper you go, the more the pump trades flow for lift. A deep well pump that also moves big volume costs more and needs more panel wattage, which is the next number.
More lift and more flow mean more watts. A small shallow pump might run on 150 to 300 watts of panel. A deep well SQFlex pulling water from several hundred feet typically wants a larger array, often in the 1,000 to 1,500-plus watt range, to hit full output through the middle of the day.
The honest answer is that panel sizing follows directly from the pump model and your head and flow, so the right order is: fix your head and daily gallons first, choose the pump, then size the array to that pump's requirement. Sizing the panels before the pump is backwards and is how people end up underpowered.
For a deep well with no grid, the Grundfos SQFlex family is built for the job. It runs directly off the panels across a wide input range and accepts wind, battery, or a generator as backup, so a cloudy week does not leave you dry.
If you already run an inverter-based solar system or want to combine solar with a grid tie, the high-efficiency Grundfos SQ Series reaches up to 250 feet at a lower price, which covers a lot of standard wells.
Browse all of these in the Solar Well Pumps collection.
For water standing up to about 160 to 240 feet, the SQ Series fits: the 10 SQ07-200 (10 GPM, 200 ft, $1,154.88) and 10 SQ07-240 (10 GPM, 240 ft, $1,221.17) are the standard home picks, with the 15 SQ10-250 (15 GPM, 250 ft, $1,292.04) for higher flow.
For water standing deeper than that, go SQFlex: the 11 SQF-2 to 395 feet ($3,099.97), or the 6 SQF-3 to 820 feet ($3,398.97) for the deepest wells.
With the right pump, up to 820 feet. The Grundfos 6 SQF-3 SQFlex is rated to that depth. For most homes, water sits far shallower than the drilled depth, so you often need less pump than you think, which is why measuring your standing water level matters.
It depends on the pump's lift and flow. Small shallow pumps run on a few hundred watts; a deep well SQFlex often needs a 1,000 to 1,500-plus watt array to reach full output midday. Choose the pump first, then size the array to its requirement.
A shallow well pump handles water within roughly 25 feet of the surface and is often a surface or jet pump. A deep well pump is a submersible that sits down in the well and pushes water up hundreds of feet. Solar deep well pumps like the Grundfos SQ and SQFlex lines are all submersibles.
Not usually. Pump to a storage tank during the day and draw from it at night. A Grundfos SQFlex can add a battery or generator as backup for stretches without sun, which is worth considering on a property where running out of water is not an option.
Most people do not know their standing water level or daily use off the top of their head, and that is fine. Give the Krato Power team your well's total depth, any pump or water-level details you have, and how many people or animals you are supplying. We will work out your head and flow and match you to the right Grundfos deep well pump. Start in the Solar Well Pumps collection.