Can solar run a borehole pump?
Yes. A solar pump controller, often called a solar VSD, lets solar panels run an ordinary borehole pump directly, without the grid and usually without batteries.
Solar panels produce DC power. The solar VSD (variable speed drive) turns that into the AC power a pump motor needs, and adjusts the pump's speed to match the sunlight. In bright sun the pump runs at full speed. When a cloud passes, it slows down instead of stopping, so you still get water, just less of it.
Borehole pumping is mostly a daytime job, which lines up neatly with the hours the panels produce power. That is why pumping is one of the most natural uses for solar on a farm.
How does a solar borehole pump system work?
The panels feed a solar VSD, the VSD drives the pump, and the pump fills a tank or dam that stores the water for later.
A typical system has five parts:
- Solar panels, usually on a ground-mount frame near the borehole.
- A solar VSD (pump controller) in a weatherproof enclosure.
- The borehole pump. In many cases an existing AC pump can stay in place.
- A tank or dam to store water for nights and cloudy days.
- Optionally, a grid or generator connection for a hybrid setup (see below).
Do I need batteries for a solar borehole pump?
Usually not. It is much cheaper to store water in a tank or dam than to store electricity in batteries.
The simplest approach is to pump while the sun shines and let your storage carry you through the night. Batteries only make sense if you genuinely need to pump at night and cannot add storage. Farms in that position often choose a solar-diesel hybrid instead, with a generator covering long cloudy spells.
How big should the solar array be?
As a rule of thumb, the solar array is about 1.3 to 1.5 times the pump motor's rating in kW.
The extra capacity covers cloudy periods, the drop in panel output on hot days and normal system losses. It also lets the pump reach full speed earlier in the morning. Here is what that rule gives for some common pump sizes:
| Pump motor | Typical solar array |
|---|---|
| 2.2 kW | About 3 kWp |
| 7.5 kW | About 10 to 11 kWp |
| 22 kW | About 30 kWp |
The controller matters too. It has to be sized for the pump's starting load, not just its running power. An undersized controller can struggle to start the pump and may wear out early.
Can it also run on Eskom or a generator?
Yes. Many solar pump controllers can switch automatically between solar and a grid or generator supply.
In a hybrid setup, solar runs the pump whenever there is enough sunlight, and the grid or generator takes over when there is not, without anyone flicking a switch. This suits farms that need water around the clock but want to cut most of their pumping costs.
Solar, diesel or Eskom: how do they compare?
Solar costs more upfront but very little to run. Diesel and Eskom cost less to start but keep costing you every month.
| Option | Solar pump | Diesel generator | Eskom connection |
|---|---|---|---|
| Upfront cost | Panels, controller and installation | The generator | Connection costs |
| Running cost | Almost none in daylight | Fuel, oil and servicing | A monthly electricity bill |
| Day-to-day effort | Runs by itself | Refuelling and maintenance | Low |
| Far from the grid | Works | Works | Only where the grid reaches |
| Pumping at night | With storage or a hybrid setup | Yes | Yes |
What does a solar borehole pump cost?
It depends mainly on the size of the pump. As an indication, systems for 5 to 16 kW pumps cost around R45 000 to R200 000.
The biggest cost drivers are the pump size (which sets how many panels you need), the controller, the mounting frame, the length of cable runs and whether you can keep your existing pump. Where solar replaces diesel, payback is often quick: around 18 to 36 months is typical.
For a first estimate, try the farm solar savings calculator, or send us your pump details for a sized quote.
Is solar pumping right for my farm?
It is a strong fit if your pump runs mostly in daylight and you are currently paying for diesel or a large Eskom pumping bill.
- Your pump runs mainly during daylight hours.
- You currently run the pump on diesel.
- Pumping is a big part of your electricity bill.
- Your pump is rated 1.5 kW or more.
- You would rather not refuel or start a generator.
If most of your pumping happens at night, start by looking at water storage or battery backup rather than a solar-direct pump.
What does this look like on a real farm?
In Wolwehoek in the Free State, a 10 kWp solar array now runs a 7.5 kW borehole pump with no fuel and no batteries.
The farm was choosing between a diesel generator and a new Eskom connection. Instead, we installed an INVT solar VSD that runs the pump straight from the panels, delivering about 12 m³ an hour into two 30 000-litre dams. Read the full Wolwehoek case study →