Solar Pumps for Deep Wells (150-300m): What You Need

The short answer: yes, a deep well solar pump can reliably lift water from wells of 150-300m — but only with a high-head multi-stage pump running on a high-voltage AC/DC system. A 150-200m domestic or farm well typically needs a pump rated for roughly 1.15x the depth as head, and models like the 4DPC12-265 (265m) or the high-speed 4DGS15-245 (350m) are built exactly for this range. The two things that decide everything are total dynamic head (TDH) and panel string voltage — get those right and a deep well solar pump is a fully practical, fuel-free alternative to a diesel genset.

How deep can a solar pump realistically go?

Deep well solar pumps handle 150-300m and beyond — the only real limit is choosing a model with enough rated head. Standard 24-48V submersible pumps top out around 100-180m, which is fine for shallow boreholes. For 150-300m depths you move into the high-head classes:

• Screw-type (progressive cavity) DC pumps reach 150-180m, e.g. 3DSS2.0-150-48-750 (150m) and 3DSS2.2-180-72-1100 (180m) — best when the water has sand.
• AC/DC multi-stage pumps reach 200-340m, e.g. 4DPC12-213-380/520-4000-A/D (213m), 4DPC12-265-390/520-5500-A/D (265m), 4DPC12-315-390/520-7500-A/D (315m), and 4HJSC11-339-380/520-7500-A/D (339m).
• High-speed (6000rpm) deep well pumps reach the furthest — the 4DGS15-245/14-18500-A/D holds a 350m head and the 4DGS15-302/17-22000-A/D reaches 426m.

A pump’s rated head is measured at its best flow point; your actual requirement is the total dynamic head, which is always higher than the well depth.

How do you calculate the head you need?

The simple rule: TDH = (well depth × 1.15) + (horizontal pipe length ÷ 10). The ×1.15 covers friction in the vertical riser and fittings; dividing the horizontal run by 10 converts its friction to an equivalent head in metres.

Example for a 200m deep well with a 50m horizontal run to a tank:

TDH = (200 × 1.15) + (50 ÷ 10)
    = 230 + 5
    = 235 m

So you need a pump rated for at least 235m of head. The 4DPC12-265-390/520-5500-A/D (265m) or 4DGS15-245/14-18500-A/D (rated 245m) both fit this case. If you pick a pump whose rated head is below your TDH, the flow rate collapses — often to near zero — because the pump cannot overcome the back pressure.

Why deep wells need high-voltage AC/DC systems

High-head pumps are high-power (3-22kW), and high power at low voltage means dangerously high current — so deep well systems should run at 380/520V DC. This is the single most important electrical decision for a deep well.

• Less cable loss: for the same power, doubling the voltage halves the current (Power = V × I). Halving the current cuts the I²R copper loss by a factor of four. On a 250m cable run this is the difference between a working system and one that wastes half its power as heat.
• Smaller, cheaper cables: lower current lets you use a thinner, more affordable submersible cable.
• Bigger panel strings: these systems run on high-voltage panel arrays (optimum input 520-650V DC), which is where multi-panel strings naturally land.

The wiring rule that protects every controller is the VOC limit — the open-circuit voltage of your panel string must stay under the controller’s max:

Step-by-step panel sizing for a 5.5kW deep well pump:

1. Apply the 1.3x rule: panel power ≥ 1.3 × 5.5kW = 7.15kW.
2. Using 550W panels, that is 7,150 ÷ 550 ≈ 13 panels.
3. Wire them in series and check the string VOC stays under the controller limit (e.g. < 780V for the 4DGS/380V series), then confirm the MPP voltage lands in the controller’s optimum window (520-650V for these systems).

Installation considerations for deep wells

Deep well installation is about cable, column pipe and the well screen — get the geometry right and the pump runs unattended for years.

• Submersible cable: size by length and current to keep voltage drop under ~5%. Use a dedicated submersible cable with a proper water-tight splice at the wellhead; a poor splice is the most common cause of deep well failures.
• Column pipe & safety rope: support the pump with a stainless steel safety rope or cable, not the power cable. Use the correct pipe diameter so friction losses stay within your TDH margin.
• Well screen / bottom clearance: keep the pump intake 3-5m above the bottom so it does not draw sand or sludge. In sandy wells, prefer a screw-type or stainless impeller pump and consider a sand separator.
• Dry-run protection: the controller’s dry-run protection is essential at depth — there is no easy manual way to watch a pump 200m down, so let the controller protect it automatically.
• Hybrid option: an AC/DC model lets you run on solar by day and switch to a generator or grid feed at night, which matters if the deep well is your only water source. See our AC/DC vs DC guide for the trade-offs.

Not sure which deep well pump matches your borehole? Message me on WhatsApp with your well depth, horizontal run and daily water need — I’ll recommend a high-head model and panel string. Or use the sizing tool to match your well to a complete pump + controller + panel set.