Solar Borehole Pumps for Farms: Converting Existing Pumps, Costs and Payback

Most commercial farms already have their boreholes, and most of those pumps run on Eskom or a diesel generator. Converting a borehole pump to solar rarely needs a new pump. A solar array feeds a solar pump drive, and the drive runs the pump you already own. The reservoir does the storing, so there is no battery, and because a borehole can wait for the sun it is usually the easiest load on a farm to move to solar.

Phoenix Energy runs the whole project for solar borehole pumps: the solar array, the WEG solar pump drive, the work on the borehole and the pump, and the installation, bought outright or on a lease. For the work down the borehole we bring in a borehole specialist, so you deal with one company throughout. This guide covers how the system works, how we size the array for winter, what pumping costs today on Eskom's Ruraflex and Landrate tariffs and on diesel, and what solar saves and how quickly it pays back. The figures are worked out for one example farm, an illustration rather than a client, and every tariff, price and design figure is dated and sourced at the end.

fixed charges per year on a Landrate 1 to 3 supply, before any energy is used (excl. VAT, 2026/27)

R36k to R77k

inland wholesale price of 0.05% sulphur diesel from 7 October 2026

R31.95/l

first-year Section 12B deduction on solar PV of up to 1 MW

100%

How a solar borehole pump works

The panels feed a solar pump drive, and the drive runs the pump. The drive, which some suppliers sell as a solar pump inverter, is a variable speed drive with maximum power point tracking built in: it takes whatever the array is producing and sets the pump's speed to match, so you get less water in the early morning and late afternoon and full flow around midday. The water goes to a tank or reservoir, which does the job a battery would do in a building.

A farm system has five parts, and we take responsibility for all of them:

• The pump and motor, down the borehole. Our borehole specialist checks the existing pump or, on a new borehole, tests the borehole and fits the pump.
• The tank or reservoir, with a level sensor that tells the drive when to stop. Most farms already have one.
• The solar array, usually ground-mounted near the borehole.
• The solar pump drive, which replaces the pump's existing control box.
• Optionally, a second supply (Eskom or a generator) for cloudy spells, wired into the same drive.

The drive does more than set the speed. WEG's CFW500 Solar Pump Drive, for example, reads the motor's torque and speed to detect a dry borehole and stops the pump before it runs dry.

Converting an existing borehole pump to solar

On most farms this is the whole job. A standard three-phase submersible pump runs from a solar pump drive just as it runs from Eskom, so the pump stays in the borehole. What changes is above ground:

• The solar pump drive takes the place of the control box.
• A ground-mounted array goes up near the borehole, sized for your winter sun.
• If you keep Eskom or a generator as backup, the same drive switches between supplies.

Two checks come first. Our borehole specialist confirms the motor's condition and the pump curve, because a worn motor, or a pump chosen for a different head, should be dealt with before the solar goes in. And any solar connected to an Eskom supply needs Eskom's approval, which matters most on a dedicated Landrate supply (see the payback section).

A new borehole is the same project with more work down the hole. Our borehole specialist drills and tests the borehole, and the yield test and the pump curve set the size of the pump, the array and the drive. Either way we work with AC pumps: standard motors and pump ends that any pump shop can supply and repair.

Is a solar borehole pump kit enough?

Solar borehole pumps come in two families, and the size of the job usually decides between them.

A solar borehole pump kit, meaning a small DC pump, a controller and a few panels sold together, does the job for a house or a single stock watering point with a shallow water level. On a commercial farm, four things call for an engineered system:

• The array has to be sized for the head, the daily volume and your June sun, not for the pump's kW rating.
• Long cable runs need the voltage drop worked out, or the motor starves.
• A farm array of a dozen or more panels in an open field needs a proper structure and protection against theft and lightning.
• A hybrid supply, Eskom or a generator, needs a drive built to switch between them.

How many solar panels a borehole pump needs: size for winter

We size the array from two figures: the daily water volume and the total head, which is the depth to the water while pumping plus the lift to the tank and the pipe friction. On an existing borehole most of this comes from the original yield test and the pump's records, and where it is missing our borehole specialist measures it on site. The yield test caps how much the borehole can give, so the daily volume has to sit within it, whatever the array could power.

For the example farm, sizing the array takes three steps:

1. Lifting the water takes 16.3 kWh a day. The energy needed is volume (m³) × head (m) ÷ 367, so 60 × 100 ÷ 367.
2. The array has to deliver 32.7 kWh a day. Pump, motor and drive lose energy on the way. The best solar pumping systems reach about 60% (World Bank, 2018), and we plan on 50% for a real installation over a real day.
3. Size the array for June. WEG's sizing rule for its solar pump drive is array watts = 1.25 × daily energy ÷ peak sun hours, taken in the worst month. We took the peak sun hours from PVGIS for north-facing panels at latitude tilt.

Bloemfontein and Worcester get almost the same sunshine over a year, but the Western Cape winter is much darker, so the same pump needs about 27% more array there. Size on the annual average and the system comes up short in winter in both regions. The common rule of thumb of 1.3 to 1.5 times the pump's kW gives 5.2 to 6 kWp here, which would not deliver 60 m³ on a June day in either place.

A tank holding two to three days of demand (120 to 180 m³ here) covers a run of cloudy days, and Eskom or a generator as backup lets you build a smaller one. The World Bank's guidance prefers water storage to batteries, as we do.

What pumping costs today: Ruraflex, Landrate and diesel

The example farm uses about 11,900 kWh a year, and what that costs depends on how the pump is powered today. On Ruraflex, the daylight hours a solar pump would take over are almost all standard time: about R2.55 a kWh averaged over 2026/27, once the network, legacy and ancillary charges are added to the energy rate. A pump that runs at night today is on cheaper off-peak time, about R2.02 a kWh on the same basis, so solar saves less there.

The Landrate column is the easiest to overlook. A borehole far from the farmhouse often has its own Eskom supply on Landrate, and every Landrate supply pays fixed charges every day whether the pump runs or not: R35,900 a year on Landrate 1 and R77,200 on Landrate 3, before a single kilowatt hour is used.

A generator big enough to start a 4 kW pump runs lightly loaded once it is going, which is where it burns the most fuel per kWh, hence the wide range. The figures use the wholesale price before the diesel refund, which since 1 April 2026 covers all eligible diesel rather than 80% of it. A farmer who claims the refund saves somewhat less than the chart shows, but diesel stays the most expensive way to pump.

Payback: what a solar borehole pump saves

The yearly saving is the cost that solar takes away. For the example farm, with the pump and the reservoir already in place:

Payback is the installed price divided by that saving, so what runs the pump today matters more than the solar hardware. A system costing R150,000, a round figure for illustration rather than a quote, pays back in about a year against diesel, about two years against a dedicated Landrate supply, and about five years against daytime pumping on Ruraflex. Ruraflex is the slowest because the farm keeps its fixed charges and only the energy cost goes. Eskom's tariffs for its direct customers rose 8.76% from 1 April 2026, and each increase shortens the payback.

Closing a Landrate supply needs care. Landrate tariffs are for supplies without grid-tied generation, and a time-of-use tariff such as Ruraflex is required where there is. If you keep the connection as backup to a solar drive, you need Eskom's approval and possibly a tariff change, and the fixed charges stay, so the saving is the energy cost only. The R73k assumes the supply is closed and the system runs off-grid, with enough storage for cloudy spells.

Tax

If you buy the system, tax deductions shorten the payback further. The array and the pump take different routes:

• The solar array: Section 12B gives a 100% deduction in the year it is brought into use for solar PV of up to 1 MW. That covers the panels, the structure and foundations, and the electrical equipment of the generating system.
• A new pump and motor: they don't generate electricity, but Section 12B also writes off machinery used in farming, over three years at 50%, 30% and 20%.
• Boreholes and pumping plants: the farming rules in the Income Tax Act allow a deduction for boreholes and pumping plants, up to the farm's taxable income from farming in that year, with any excess carried forward to the next year. SARS explains the rule in section 3.6.1 of its guide to the taxation of farming operations (IT35).

Buying or leasing

You can buy the system outright, or spread the cost through a Power Lease Agreement: fixed monthly payments over 5 to 10 years, nothing up front, and the system is yours at the end of the term. On a lease the test is cash flow rather than payback, because the monthly payment should sit below the monthly saving. For the example farm, that is the saving in the chart divided by twelve:

• Against diesel: about R9,500 to R16,000 a month.
• Against a dedicated Landrate supply: about R6,000 a month.
• Against Ruraflex: about R2,000 to R2,500 a month.

The diesel and Landrate savings leave room for a lease payment. The Ruraflex saving would barely cover one, so on the main farm supply, buying outright and claiming the Section 12B deduction usually makes more sense. Our guide to solar financing for business compares cash, loans, leases and PPAs.

Solar for farms: every pump on the farm

A farm has several pumps, and each one has its own job and its own schedule. The borehole pump lifts water into the reservoir, and because the reservoir stores it, the pump can run whenever the sun shines. Irrigation pumps then move that water from the reservoir or dam out to the lands, with booster pumps holding the pressure in the lines. They run when the crop needs water, often at night or in the early morning to cut evaporation, so they cannot simply follow the sun.

Taken together, pumps are often among the largest electricity loads on an irrigated farm. Many farms also run them from several dedicated Eskom connections, one at each pumping point, and each of those pays its own fixed charges whether its pump runs or not. How the pumps run sets much of the farm's energy bill.

That is why we look at every pump on the farm. A high-efficiency WEG motor uses less energy for the same work, and a variable speed drive runs a pump at the speed the flow and pressure call for, instead of running it flat out against a throttled valve. That is our Energy Optimisation work. Solar then takes the pumping that can run in daylight, starting with the boreholes. Moving them first takes a flexible load off the main supply, and the farm's main solar and storage system can then be sized around what is left.

WEG is our technology partner across all of it: motors, variable speed drives and solar pump drives. Its solar pump drives run from the CFW500 Solar Pump Drive up to the ADV200 SP, which covers pumps from 1.5 kW to 1.8 MW and takes Eskom or a generator as backup.

Frequently asked questions

Can I add solar to my existing borehole pump?

Usually, yes, and you keep the pump you already own. A standard three-phase submersible pump can run from a solar pump drive, which replaces the control box and takes the array as its main supply. A hybrid drive keeps Eskom or a generator as backup. Before the solar goes in, our borehole specialist checks the motor's condition and the pump curve, and any solar on an Eskom supply needs Eskom's approval. We handle the whole conversion: the array, the WEG drive and the work on the pump.

How much does a solar borehole pump cost in South Africa?

On the example farm in this guide (a 4 kW pump lifting 60 m³ a day against 100 m of total head), a system of about R150,000, a round figure for illustration rather than a quote, pays back in about a year against diesel, about two years against a closed Landrate supply and about five years against daytime pumping on Ruraflex. Every farm is priced per site, because the head, the daily volume and the winter sun set the size of the array. If the farm already has a working pump, it stays, and the cost is the array, the drive and the installation.

How many solar panels does a borehole pump need?

It depends on the daily volume, the head and your winter sun more than on the pump's kW. On the example farm, a 4 kW pump lifting 60 m³ a day against 100 m of total head needs 14 panels of 550 W in the Free State and 17 in the Western Cape. The formula is array watts = 1.25 × daily energy ÷ peak sun hours in the worst month.

What size solar pump do I need for my borehole?

If the farm already has a pump that suits the borehole, you may not need a new one: the array and the drive are sized around it. For a new borehole, we choose the pump from the yield test, the daily volume and the total head, using the pump's curve rather than its kW rating. The example farm uses a 4 kW pump for 60 m³ a day at 100 m of head.

Do solar borehole pumps work on cloudy days?

Yes, at reduced flow. The drive slows the pump to match the power available, so a cloudy day delivers less water. A centrifugal pump stops below a threshold speed, so under heavy overcast it may not run at all. That is why the reservoir holds two to three days of demand, or the drive has a generator or Eskom as backup.

Do solar borehole pumps need batteries?

Almost never. The tank covers the hours and days without sun, which is why solar pumping guidance, the World Bank's included, prefers tank storage to batteries. A battery earns its place only where water must be pumped at night and there is no room for a tank.

Can a solar borehole pump run at night?

Not from the panels. To pump at night you need a second supply on a hybrid drive, either Eskom or a generator, or a battery. Most farms pump by day and draw from the reservoir at night.

How long do solar borehole pumps last?

The array lasts longest, and 20 years is a common planning life for the whole system (World Bank, 2018). The pump is the part that wears, and the same guide expects it to be replaced after 7 to 10 years. Plan for one pump replacement within the life of the array.

Sources

• Eskom, Tariffs and Charges Booklet 2026/2027: Ruraflex (p. 32), Landrate (p. 37), time-of-use periods (Appendix A), 8.76% increase from 1 April 2026.
• Minister of Mineral and Petroleum Resources, fuel price adjustment effective 7 October 2026, gov.za, 5 October 2026; inland 0.05% diesel price as reported by BusinessTech, 5 October 2026.
• SARS, diesel refund on 100% of eligible diesel for on-land farming from 1 April 2026, 20 April 2026.
• SARS, Guide IT39 on allowances for assets used in generating electricity, 23 November 2024.
• SARS, Guide IT35 on the taxation of farming operations, 13 October 2023.
• World Bank, Solar Pumping: The Basics, 2018 (copy held by the SuSanA library).
• WEG, CFW500 Solar Pump Drive application manual, February 2025; ADV200 SP brochure, January 2023.
• European Commission JRC, PVGIS v5.3, queried 12 October 2026.
• Cummins, C33 D5 generator set data sheet (fuel consumption by load).