Choosing a Solar System for a Borehole Pump

A solar-powered borehole can provide reliable water for a home, farm, livestock or business without depending entirely on ZESA or a generator. However, getting good results requires more than buying a pump and connecting it to several solar panels.

The pump, panels, controller, cabling, protection equipment, pipework and water storage must work as one correctly sized system.

A system that is too small may run but fail to deliver enough water. An oversized system may work, but it can add unnecessary expense. Incorrect voltage, poor protection or an unsuitable pump can also damage equipment and leave the property without water.

This guide explains how to choose a solar system for a borehole pump in Zimbabwe using the information that matters most.

Start with the amount of water you need

Before choosing the pump or panels, estimate how many litres of water the property needs each day.

Water may be required for:

Household use
Livestock
Vegetable gardens
Drip irrigation
General crop irrigation
Construction
Commercial operations
Filling a storage tank
Supplying several homes

A household and a commercial farm can use the same size borehole but have completely different daily water requirements.

Your estimate should account for the busiest realistic day rather than only average consumption. It should also include reasonable allowance for future demand if the property is likely to expand.

For irrigation, consider the area being watered, crop requirements, irrigation method and seasonal conditions. Drip irrigation may require less water and pressure than sprinklers covering a large area.

Obtain reliable borehole information

The next step is collecting accurate information about the borehole.

Important measurements include:

Total drilled depth
Static water level
Dynamic or pumping water level
Sustainable borehole yield
Borehole casing diameter
Recommended pump installation depth
Water quality, where relevant

Static water level

The static water level is the distance from ground level to the water when the pump is not operating.

Dynamic water level

The dynamic water level is the water level while pumping. It is normally lower than the static level because water is being removed from the borehole.

The dynamic level is particularly important when selecting the pump. A system designed using only the static level may perform poorly once pumping begins.

Borehole yield

The yield indicates how much water the borehole can sustainably provide, commonly expressed in litres per hour.

Installing a pump that removes water faster than the borehole can replenish it may cause the water level to fall until the pump runs dry. Dry-run protection can stop the pump before it is damaged, but it cannot increase the borehole’s yield.

A recent borehole-capacity test gives the installer much better information than estimating from the drilled depth alone.

Calculate the total dynamic head

The pump does not only lift water from inside the borehole. It may also need to push it uphill, raise it into a tank and overcome resistance through the pipe.

The total resistance is known as the total dynamic head.

It can include:

The pumping water level in the borehole
The vertical height from the borehole to the tank
Additional elevation along the delivery route
Pressure required by the irrigation or plumbing system
Friction losses through pipes, bends, fittings and valves

For example, water may be drawn from a pumping level 45 metres below ground and delivered into a tank 10 metres above the borehole. The vertical lift is already approximately 55 metres before pipe friction and required outlet pressure are included.

A long, narrow pipe creates more resistance than a correctly sized pipe. Therefore, distance and pipe diameter affect the pump selection even where the ground appears relatively flat.

Do not choose the pump by horsepower alone

One of the most common mistakes is choosing a borehole pump using horsepower without checking its performance curve.

Two 1HP pumps can produce very different results. One may provide a higher flow at a low head, while another is designed to move less water against a much higher head.

Important pump specifications include:

Rated power
Operating voltage
Maximum head
Maximum flow
Expected flow at the required head
Outlet size
Pump diameter
Motor type
Controller requirements

Maximum head and maximum flow should not be considered simultaneous performance figures.

At its maximum head, a pump may deliver little or no usable flow. Its maximum flow generally occurs when it is working against a much lower head.

The correct approach is to compare the required operating point with the manufacturer’s pump-performance curve.

Choose between an AC and DC solar pump

Once the required flow and pumping head are known, you can consider whether an AC or DC pump is more appropriate.

A DC solar pump is commonly connected to panels through a dedicated pump controller. This arrangement can be efficient and relatively straightforward for solar-direct operation.

An AC pump requires a suitable solar pump inverter or variable-frequency drive to convert the panels’ DC electricity into AC electricity for the motor.

A DC system may suit:

Remote off-grid properties
Household water supply
Livestock watering
Smaller irrigation projects
Solar-direct daytime pumping
Systems that fill a storage tank

An AC system may suit:

Higher water demand
Deep or demanding boreholes
Larger irrigation systems
Existing compatible AC pumps
Sites requiring ZESA or generator backup
Commercial water-supply applications

Neither option is automatically better. The correct choice depends on the required duty point, available equipment, backup requirements and long-term access to replacement parts.

Read our detailed comparison of AC and DC solar borehole pumps before deciding between the two arrangements.

Match the panels to the pump controller

After selecting the pump and controller, the solar array must be designed around their electrical requirements.

Important specifications include:

Required operating power
Minimum starting voltage
Maximum input voltage
Recommended operating voltage
Maximum input current
Panel open-circuit voltage
Panel operating voltage
Panel operating current
Temperature-related voltage changes

Solar panels may be wired in series to increase voltage or in parallel to increase current. The correct arrangement depends on the controller.

Connecting too few panels may prevent the pump from starting reliably or cause it to stop during weaker sunlight. Connecting too many panels in series can exceed the controller’s maximum voltage and damage it.

The number of panels should not be determined by dividing the pump’s wattage by the wattage printed on one panel. Real operating conditions, system losses, sunlight variation and the controller’s voltage range must also be considered.

Our guide to solar panels for boreholes in Zimbabwe explains these considerations in greater detail.

Should the solar array be oversized?

A carefully designed solar array may have more rated panel capacity than the pump motor’s headline power.

This does not necessarily mean the system is incorrectly oversized. Additional panel capacity can help:

Start pumping earlier in the morning
Continue operating later in the afternoon
Improve performance under light cloud
Compensate for heat and normal system losses
Deliver the required daily water volume more reliably

However, the array must remain within the pump controller or solar pump inverter’s permitted electrical limits.

Adding panels without checking voltage and current is unsafe. The design must follow the specifications of the exact controller being installed.

Use water storage instead of batteries where practical

Most solar borehole-pumping systems do not need electrical batteries.

The pump can operate during daylight and transfer water into a storage tank. Water is then available at night or during periods of weaker sunlight.

This approach uses the tank to store water rather than storing electricity in batteries.

It can reduce:

Initial system cost
Battery replacements
Energy-conversion losses
Maintenance requirements
System complexity

The storage tank should be sized according to daily demand, expected pumping hours and the level of reserve required during cloudy weather or maintenance.

A tank-full float switch can automatically stop the pump when the tank reaches the required level. This prevents overflow and unnecessary pump operation.

Where pumping must continue at night, a compatible generator, ZESA supply or battery system may be considered. The pump’s starting and running requirements must be included in the design.

Select the right tank position

The location and height of the tank affect both pump sizing and water pressure.

A higher tank increases the head against which the borehole pump must work. However, it can also provide more gravity pressure to the property after the water has been stored.

The designer should consider:

Tank height above the borehole
Distance between the borehole and tank
Elevation changes along the route
Required pressure at taps
Irrigation pressure
Structural strength of the tank stand
Accessibility for maintenance

An extremely high tank stand should not be used as a substitute for a correctly designed pressure or booster-pump system.

The cost of the tank and supporting structure should also be included when budgeting for the complete water system.

Check the borehole casing and pump diameter

A pump must physically fit inside the borehole casing while allowing enough space for installation, cooling and removal.

The selected equipment should account for:

Internal casing diameter
Pump diameter
Motor cooling requirements
Submersible cable
Delivery pipe
Safety rope
Water-level sensors

The pump must also be installed at the correct depth.

Placing it too high may expose it when the water level falls. Installing it too close to the bottom can increase the risk of drawing sediment into the pump.

The installer should follow the borehole report and the pump manufacturer’s installation instructions.

Use the correct delivery pipe

The delivery pipe affects water flow, system pressure and total dynamic head.

A pipe that is too narrow creates unnecessary friction. This forces the pump to work against additional resistance and can reduce the amount of water reaching the tank.

The pipe should be selected according to:

Required flow rate
Total length
Pump outlet size
Operating pressure
Installation depth
Exposure to sunlight
Water quality
Underground or above-ground installation

Fittings, non-return valves and bends must also be suitable for the expected pressure.

A cheaper undersized pipe can reduce the performance of an otherwise well-selected pumping system.

Install dry-run and tank-full protection

Dry running occurs when the pump operates without enough water around it. This can cause overheating and damage.

A suitable system may use:

A borehole water-level probe
A dry-run sensor
Controller-based dry-run detection
Automatic restart after water recovery

Tank-full protection is also important. A float switch tells the controller to stop pumping when the storage tank is full.

These controls help prevent pump damage, wasted water and unnecessary operation.

The controller and sensors must be compatible with each other and correctly configured during commissioning.

Include electrical protection

Solar borehole pumps operate outdoors and may be exposed to lightning, surges, moisture and unstable backup supplies.

Depending on the system, protection may include:

DC fuses or circuit breakers
DC isolators
AC breakers
Surge-protection devices
Correct earthing
Lightning protection
Motor overload protection
Overvoltage and undervoltage protection
Weather-resistant controller housing

Long cables can increase exposure to induced surges during thunderstorms. Correct earthing and surge protection should therefore be treated as essential parts of the installation.

Learn how solar protection kits reduce damage from lightning, power surges and ZESA faults.

Use the correct cable sizes

Cable size affects voltage drop, pump performance and safety.

The installer must consider:

Pump power
Operating voltage
Current
Distance from panels to controller
Distance from controller to pump
Installation method
Cable temperature rating
Maximum acceptable voltage drop

A cable that is too small can cause energy loss, overheating and unreliable starting.

Submersible connections must be properly waterproofed. Ordinary electrical tape is not an acceptable long-term method for a cable joint that will remain underwater.

Decide whether backup power is necessary

A solar-direct pumping system operates when sufficient solar energy is available. This may be adequate where water is pumped into a suitably sized tank.

Backup power may be important for:

Commercial farming
High livestock demand
Community water supplies
Properties with limited storage
Critical operations
Pumping after sunset

Some AC solar pump inverters can accept power from solar panels, ZESA or a generator. Certain specialised DC systems also support alternative power through compatible equipment.

Backup compatibility should be confirmed before purchase. An AC supply must never be connected directly to a DC pump unless the system includes approved conversion equipment.

Consider seasonal conditions

A system should not be designed only around ideal midday sunshine.

Solar production changes with:

Time of day
Season
Cloud cover
Panel temperature
Dust and dirt
Panel orientation
Shading

The required daily water volume must still be achievable during the relevant operating season.

For farming, water demand may be greatest during hot and dry periods. Fortunately, those periods may also provide strong solar conditions, but this relationship should not be assumed without considering the specific location and application.

The FAO notes that water availability, crop requirements, panels, pumps and irrigation infrastructure must be designed as one system.

Panels should also be cleaned when dust significantly reduces performance. Our guide explains how to maintain solar panels in Zimbabwe’s dusty climate.

Avoid shading on the solar panels

Even partial shading can reduce solar-array output.

Inspect the installation area for:

Trees
Buildings
Water tanks
Poles
Antennas
Future construction
Seasonal changes in the sun’s path

The panels should face an appropriate direction, be mounted at a suitable angle and receive strong sunlight during the main pumping period.

The mounting structure must also withstand wind and protect the panels from theft or accidental damage.

Ground-mounted arrays are common for borehole-pumping systems because they can be installed near the pump equipment and positioned for good solar exposure. However, they must be securely mounted and protected from livestock, vehicles and unauthorised access.

Plan for maintenance and replacement parts

A reliable system should be serviceable after installation.

Ask the supplier:

Is the pump brand supported locally?
Is a replacement controller available?
Are water-level and tank sensors replaceable?
Can the pump be removed without damaging the pipe or cable?
Is the controller’s manual available?
Who can diagnose error codes?
What does the warranty cover?
Are commissioning settings documented?

A cheap system may become expensive if a failed controller cannot be replaced or if the entire pump must be changed because one component is unavailable.

Solar Power Shop supplies various water-pumping options, including solar DC pumps and complete water-pumping packages.

Common mistakes when choosing a borehole solar system

Choosing by horsepower only

Horsepower does not show how much water the pump will deliver at your required head.

Ignoring the dynamic water level

A pump selected using the static level may struggle when the water level falls during operation.

Buying panels before selecting the controller

The array voltage and current must match the controller’s permitted range.

Installing too little water storage

A small tank can leave the property without water at night even when the pump performs correctly during the day.

Using undersized cables

Long, thin cables create voltage loss and may prevent reliable pump operation.

Ignoring pipe friction

Narrow pipes and long delivery routes can substantially increase the system’s total head.

Excluding protection equipment

Saving money by omitting isolators, surge protection or earthing can expose expensive equipment to damage.

Buying before conducting a site assessment

A generic package may need different panels, cables, piping or controls once the borehole and property are assessed.

For additional examples, read about common Dongyin solar-pump installation mistakes and how to avoid them.

What should a complete quotation include?

A detailed quotation should identify:

Pump make and model
Pump power and voltage
Expected flow at the required head
Pump controller or solar pump inverter
Number and rating of solar panels
Panel configuration
Mounting structure
Electrical protection
Water-level and tank sensors
Submersible cable
Delivery pipe and fittings
Installation labour
Transport or delivery
Testing and commissioning
Warranty information
Items excluded from the quotation

Do not compare quotations using the final amount alone. Confirm whether they include the same equipment, materials, controls and installation work.

Solar Power Shop charges installation separately because labour and site-specific materials depend on the borehole and property. Delivery may also be charged depending on the location.

Our guide to solar installation costs in Zimbabwe explains why site conditions affect the final quotation.

Information to provide when requesting a quotation

To receive a useful recommendation, provide:

Borehole location
Total borehole depth
Static water level
Dynamic water level
Tested borehole yield
Borehole casing diameter
Required litres per day
Intended use of the water
Distance from borehole to tank
Tank height
Pipe route and elevation changes
Existing pump information, if applicable
Availability of ZESA or a generator
Whether pumping is required at night
Any existing solar panels or pumping equipment

Photos of the borehole area, tank position and proposed solar-panel location can also assist with the initial assessment.

Frequently asked questions

How many solar panels are needed for a borehole pump?

The number depends on the pump’s power, operating voltage, controller limits, pumping head, daily water requirement and available sunlight. Horsepower alone is not enough to calculate the array.

Can a 1HP pump run directly from solar panels?

It can if it is designed for solar-direct operation or connected through a compatible controller or solar pump inverter. The correct voltage, current and protection requirements must be followed.

Does a solar borehole pump need batteries?

Not necessarily. Many systems pump into a water-storage tank during daylight, making water available after sunset without electrical batteries.

Can an existing borehole pump be converted to solar?

A suitable AC pump may sometimes be operated using a correctly sized solar pump inverter. Its motor specifications, condition, required head and starting requirements must first be assessed.

Can solar panels power both the house and borehole pump?

Yes, but the entire system must be designed for the combined loads. A dedicated solar-pumping array is often simpler and prevents household consumption from reducing water-pumping performance.

Is a DC pump better than an AC pump?

Not in every situation. DC pumps are often suitable for solar-direct systems, while AC pumps can offer a broader range and easier backup-power integration. The correct option depends on the borehole and water demand.

How large should the water tank be?

Tank size depends on daily consumption, pumping output, available solar hours and the amount of reserve required. It should be selected as part of the complete pumping-system design.

Can I install a solar borehole pump myself?

A simple packaged system may appear straightforward, but incorrect sizing, wiring, waterproofing or protection can damage the equipment. Professional assessment and installation are recommended, particularly for deep boreholes and higher-power systems.

Get a correctly sized borehole solar system

A reliable borehole solar system begins with accurate information—not a guess based on pump horsepower or the number of panels.

Solar Power Shop supplies borehole-pumping solutions for homes, farms, livestock and businesses throughout Zimbabwe. Customers can visit any Solar Power Shop branch or make an enquiry online.

Installation and site-specific materials are quoted separately. Delivery charges may apply depending on the location.

To receive a suitable recommendation, request a custom quotation and provide your borehole depth, water levels, tested yield, tank height, delivery distance and required daily water volume.