Solar Borehole Pumps
Cape Town

Solar borehole pumping replaces the grid connection with a solar array. The pump does the same job, but it runs when the sun is available rather than whenever a switch is thrown - and that single difference shapes the entire system design.

It suits some situations extremely well and others poorly. This page covers how it works, where it makes sense, and the practical trade-offs worth understanding before committing.

How Solar Borehole Pumping Works

A solar pumping system has four parts, and the design logic is different from a mains system:

1. 1The solar array converts sunlight into DC electricity. Array size is determined by the pumping work required - flow multiplied by head - not by the pump's nameplate rating alone.
2. 2The controller conditions the power and manages the pump. Most use maximum power point tracking to extract as much as possible from the array as light conditions change through the day, and they typically include dry-run protection and level control inputs.
3. 3The pump is a submersible unit, either a DC pump designed for solar or a standard AC pump driven through an inverter-type controller. It varies its speed with available power rather than running at one fixed rate.
4. 4Storage collects the output. This is the key design point - solar systems store water rather than electricity, filling a tank through the day so water is available whenever you need it.

That last point is what makes solar pumping practical. Rather than fitting batteries to run a pump at night, the system pumps into a storage tank during daylight and the property draws from the tank around the clock. Storing water is far cheaper than storing electricity, and a tank has a much longer life than a battery bank.

Where Solar Pumping Works Well

• Off-grid sites - remote boreholes, farm and smallholding positions where bringing in a grid connection would be expensive
• Boreholes far from a distribution board, where the cost of trenching and cabling to the borehole rivals the cost of an array
• Livestock watering, where steady daily volume into a reservoir matters more than on-demand pressure
• Irrigation into storage, where the tank buffers between the pumping profile and the irrigation schedule
• Sites with unreliable supply, where the borehole must keep working through outages
• Modest, steady daily volumes rather than large instantaneous flows

Where It Works Less Well

• Direct pressure systems without storage. Solar output varies through the day and disappears at night. Feeding fixtures directly from a solar pump gives inconsistent pressure and no supply after dark.
• Very deep boreholes with high demand. Pumping work rises with both head and volume, and the array grows accordingly. There is a point where the array size becomes impractical or the cost stops making sense.
• Shaded or constrained sites. Panels need unobstructed sun for most of the day. Trees, buildings and slopes that shade part of the array reduce output disproportionately.
• Sites where mains is already at the borehole. If a suitable supply is already there, the case for solar rests on running cost savings alone, which lengthens the payback considerably.
• Applications needing guaranteed daily volume regardless of weather. Output falls on overcast days, and a run of poor weather means less water.

Sizing a Solar Borehole System

The design sequence is the same as any borehole system, with solar-specific steps added:

1. 1Establish sustainable yield from yield testing. Solar changes nothing about this - you still cannot take more than the borehole gives.
2. 2Establish total head - pumping water level, lift to the tank, friction losses in the pipe run.
3. 3Define required daily volume, in litres per day rather than instantaneous flow. This is the figure solar systems are designed around.
4. 4Determine peak sun hours for the site in the critical month, allowing for shading, orientation and tilt.
5. 5Calculate the pumping work - the combination of volume and head determines the energy required per day.
6. 6Size the array to deliver that energy in the available sun hours of the critical month, with margin for losses, temperature effects and panel soiling.
7. 7Select pump and controller matched to the array voltage and the duty point.
8. 8Size storage to cover both daily use pattern and a realistic number of consecutive low-output days.

Note that head has a large effect. Doubling the head roughly doubles the energy needed for the same volume, which means doubling the array. This is why solar suits shallower boreholes with moderate demand better than deep boreholes with high demand.

Solar, Grid or Hybrid

Configuration	How it behaves	Best suited to
Solar only	Pumps during daylight into storage. No output at night or in poor weather.	Off-grid sites, livestock and irrigation with adequate storage, where a run of low-output days can be absorbed.
Solar with grid backup (hybrid)	Runs on solar when available, switches to mains when needed to maintain supply.	Sites with a grid connection that want the running cost saving without accepting weather risk.
Solar with generator backup	Solar primary, generator for extended poor weather or peak requirement.	Remote sites with critical supply, such as livestock, where running dry is not acceptable.
Grid only	Conventional mains-powered submersible pump.	Sites where mains already reaches the borehole and demand is high relative to head.

Hybrid arrangements are often the practical middle ground on properties that already have power. They capture most of the running cost benefit while removing the weather dependence, at the cost of a more complex control arrangement.

Practical Considerations

• Panel mounting and orientation. Fixed arrays are simplest. Orientation and tilt matter, and shading from trees or structures at any time of day disproportionately reduces output.
• Security. Solar panels in an exposed rural position are a theft target. Mounting arrangements, positioning and physical security need thought at design stage rather than after an incident.
• Soiling. Dust and bird droppings reduce output. Panels need periodic cleaning, and a position that makes that practical.
• Space. An array needs unshaded area, which is straightforward on a farm and more constrained on a suburban property.
• Controller siting. Weatherproof, ventilated and accessible, and protected from heat.
• Lightning and surge protection, particularly on exposed rural installations.
• Component availability. Some solar pump systems use proprietary controllers, which matters for parts and support years later. Ask about it before buying.

What Affects Solar Pumping Cost

• Total head - the single biggest driver, because it determines the energy and therefore the array size
• Required daily volume, which multiplies with head to set the pumping work
• Array size, panel specification and the mounting structure
• Pump and controller type, and whether the system is DC or AC through an inverter controller
• Storage capacity, which usually needs to be larger on a solar system than on a mains one
• Mounting, security measures and cabling from array to controller
• Whether the system is solar-only, hybrid, or has generator backup
• Site access and installation conditions

Where the alternative is trenching and cabling a long distance to the borehole, the comparison often favours solar on installed cost alone, before running costs are considered. Where mains already reaches the borehole, the case rests on running cost savings and the payback period is longer.

Related Borehole Services

Solar array sizing depends on total head, and head depends on how deep the borehole is - so the drilling outcome drives the cost of the solar system. Borehole Drilling Cape Town explains what determines depth in different parts of Cape Town.

What Solar Borehole Pumping Costs

Solar cost is driven by pumping work - head multiplied by daily volume - because that sets the array size, and the array is the expensive part. Doubling the head roughly doubles the energy needed, so depth matters more here than on a mains system.

Item	Indicative range	What moves it
Small DC solar pump kit	R6,000 – R22,000	Shallow borehole, modest daily volume. Pump and controller, panels sometimes extra.
Mid-range branded pump and controller	R14,000 – R55,000	Deeper duty, better efficiency and parts support. Check whether the controller is proprietary.
Solar panels and mounting	R6,000 – R45,000	Array size for the pumping work, sized against the worst month rather than the best.
Complete small domestic solar system	R35,000 – R75,000	Pump, controller, array, mounting and installation.
Complete farm or high-volume system	R70,000 – R140,000+	Larger arrays for sustained daily volume at depth.
Storage tank or reservoir	See tank costs	Essential rather than optional on solar - you store water, not electricity.
Security and theft protection for the array	R2,000 – R15,000	Worth designing in from the start on exposed rural sites.

Solar Borehole Pump FAQs

Get a Solar Borehole Pump Quote