Solar Submersible Pumps

When the water is too deep for a surface pump, a solar submersible pump lifts it straight from the borehole or well. Powered by solar panels, with no battery and no mains connection, it fills your tank or irrigates whenever the sun shines.

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Solar submersible water pumps: lifting water from a borehole or deep well

A solar submersible pump sits directly in the water, down the borehole or well. Instead of sucking water up like a surface pump, it pushes it upwards, so it can reach water lying tens of metres below ground. Solar panels power a controller at the surface, usually with maximum power point tracking (MPPT), which drives the pump motor.

With no battery, the pump runs with the sun: it delivers more in the sunniest hours and stops at night. Best practice is to store water rather than electricity: the pump fills a tank or reservoir during the day, and the water is there whenever you need it.

Stainless steel solar submersible borehole pump next to the borehole head, with solar panels, pump controller and water tank in a field — Typical set-up: submersible borehole pump, solar panels, solar pump controller and water storage (illustration).

Submersible pump or surface pump?

It all depends on how deep the water is while the pump is running. A surface pump sucks water up: once there is more than 7–8 m between the water level and the pump, it can no longer lift it, however powerful it is. For a pond, tank, river or shallow well, a solar surface water pump remains the simplest option. For a borehole or deep well, you need a submersible pump.

Comparison diagram: a surface pump draws water from up to 7–8 m below it, a submersible pump pushes water up from the bottom of a deeper borehole — The depth of the water while pumping, not the depth of the borehole, decides which type of pump you need.

What is a solar submersible pump used for?

Irrigation and drip lines: watering a vegetable plot, orchard or field from a borehole, with no power line.
Livestock watering: supplying a trough or a reserve out in the pasture, far from any socket.
Off-grid homes and sites: filling a header tank or storage tank that then supplies the building.
Water storage: filling a flexible water tank during the day so water is available when you need it.

Large farm needs? To irrigate large areas or supply livestock, our 6″ agricultural solar submersible pumps (up to 130 m³/h) and 8″ high-flow pumps (up to 160 m³/h) are available on quotation, after sizing.

How to choose a solar submersible pump

Gather this information before comparing models:

Inside diameter of the borehole: pumps are sized by diameter, often 3 inches (about 75 mm) or 4 inches (about 100 mm). The casing must be wider than the pump, with room for the cable and pipe.
Water level while pumping: the static level at rest and, above all, the lower dynamic level reached while pumping. That is the one that counts for total head.
Borehole yield: the pump must not draw more water than the borehole supplies, otherwise the level drops until the pump runs dry.
Water need: daily water volume ÷ hours of good sunshine = the flow you need.
Total head: worked out as shown in the diagram below.
Solar supply: panel power and voltage compatible with the controller, as stated on the product page.

Working out the total head of a submersible pump

Diagram: total head of a solar submersible pump must exceed H1 + H2 + 10% of L, with H1 from the lowest water level to ground, H2 from ground to the outlet into the tank and L the pipe length — H1: lowest water level to ground · H2: ground to outlet · L: pipe length.

The total head must exceed H1 + H2 + 10% of L. Example: water 30 m below ground while pumping, tank 5 m above the borehole head, 100 m of pipe → total head above 30 + 5 + 10 = 45 m. Add 10 m per bar of pressure needed at the outlet. Then go by the flow the pump delivers at that head on its curve, never its maximum flow. The three-step method is explained in our solar pump sizing guide.

Installation and protection

Hang the pump on a stainless steel safety rope and set it below the dynamic level, without resting it on the bottom of the borehole, so it does not draw in sand and sediment.
Use a submersible power cable sized for the length, and a rising main rated for the pressure.
Fit a non-return valve and dry-run protection (level probe or controller function).
Stop the pump when the tank is full, with a float switch wired to the controller where it allows.
Protect the panel circuit with a DC isolator or DC circuit breaker.

Check these points in the manual supplied with the equipment; electrical connections must be made with the power off, by a qualified person.

Frequently asked questions

Does a solar submersible pump need batteries?

No. It runs straight from the panels during the day. To have water in the evening or at night, store the water in a tank rather than the electricity in batteries.

How deep can a solar submersible pump pump from?

It depends on its maximum head, shown on the product page. The deeper the water and the longer the pipe, the lower the flow: read the flow on the curve at your total head.

What borehole diameter do I need?

The casing must be wider than the pump: a 3-inch pump for small diameters, a 4-inch pump for wider boreholes, with room for the cable and pipe.

How many solar panels does a submersible pump need?

It depends on the pump power and on its controller’s voltage range. Plan a peak panel power above the motor power to cover losses and less sunny hours.

What happens if the borehole runs dry?

Without protection, the pump runs dry and is damaged. A level probe or the controller’s protection stops it; also choose a flow that matches the borehole yield.

Submersible or surface pump for a well?

If the water stays less than 7–8 m below the pump while pumping, a surface pump may be enough. Any deeper and you need a submersible pump.

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