Solar Pump Size Guide: How to Choose a Solar Water Pump
A solar water pump gives you free water from the sun with no electricity bill and no load shedding worries. This guide explains the types of solar pumps, how to size the pump and panels and what else you need. WhatsApp us on 061 744 1001 with your borehole depth, height to the tank and daily water need, and we will size a complete kit for you.
Which type of solar pump do I need?
| Use | Best option | Shop |
|---|---|---|
| Garden, livestock troughs and small homes | Small DC solar borehole pump, 180 – 1200 W | 3HR, 3HRI, 3LARS and 3LSS pumps |
| Homes and smallholdings, deeper boreholes | 4″ low-voltage DC kit, 48 – 110 V | 4SD low-voltage DC kits |
| Water day and night, or cloudy areas | Hybrid AC/DC kit (solar plus Eskom, generator or inverter) | 4SD TGP hybrid kits |
| Farms and irrigation with a 380 V pump | Solar pump inverter for an existing three-phase pump, 4 – 22 kW | Solar pump inverters |
| House water pressure | Solar booster pump | SQB250 solar booster combo |
| Swimming pools | DC or hybrid solar pool pump | Solar pool pumps |
Step 1: Work out how much water you need per day
Add up the daily need: about 200 litres per person, plus garden, and livestock (a cow drinks about 50 – 80 litres a day). Because the pump only runs while the sun shines, divide the daily need by about 6 hours to get the flow you need. Example: 6,000 litres a day ÷ 6 hours = 1,000 litres per hour (1 m³/h).
Step 2: Work out the total head
Total head is the pump installation depth plus the height to the top of the tank plus pipe friction (roughly 1 m for every 10 m of pipe). Example: pump at 50 m, tank stand 5 m, 40 m of pipe = about 59 m. Choose a pump that delivers your flow at that head, not at its maximum head. Our borehole pump size guide explains this in more detail.
Step 3: Size the solar panels
The solar array should be about 1.3 to 1.5 times the pump power, so a 750 W pump normally runs on about 1,000 – 1,100 W of panels. The panel string voltage must fall inside the controller’s input range: too low and the pump will not start, too high and the controller can be damaged. Face the panels north at about 25 – 30° tilt and keep them out of shade.
Step 4: Store water, not electricity
Solar pumps do not need batteries. Pump into a tank that holds 2 – 3 days of water so you are covered on cloudy days, and fit a float switch so the pump stops when the tank is full. If you also need to pump at night, choose a hybrid AC/DC kit that runs on Eskom, a generator or your home inverter.
Step 5: Protect the system
Solar pump controllers include dry-run protection, which stops the pump if the borehole level drops. Earth the panel frames and controller properly, use cable rated for DC and the correct thickness for the distance (see our cable sizing chart), and keep the controller out of direct sun and rain. Spares are in solar range spares.
DC low-voltage, hybrid or solar inverter?
Low-voltage DC kits (48 – 110 V) are efficient, safer to work on and need fewer panels, which makes them ideal for homes and smallholdings. Hybrid AC/DC kits use a brushless DC motor with a controller that accepts both solar and AC power, so you get water any time. Solar pump inverters convert an existing three-phase AC borehole or surface pump to solar, which is the most cost-effective route for larger farm and irrigation pumps.
Frequently asked questions
Do solar water pumps need batteries?
No. Solar pumps run directly from the panels during the day and fill a storage tank, so the water in the tank is your “battery”. Hybrid AC/DC models can also run from Eskom, a generator or an inverter at night or on cloudy days.
How many solar panels do I need for my pump?
As a rule of thumb the solar array should be about 1.3 to 1.5 times the pump power, and the panel voltage must fall within the controller’s input range. We size the panels with the pump so the string voltage is correct.
How much water does a solar borehole pump deliver per day?
It depends on the pump, the head and the sun. In South Africa a solar pump typically pumps for 6 to 8 useful hours a day, so multiply the pump’s flow at your head by about 6 hours for a safe daily estimate.
Will a solar pump work on cloudy days?
It will pump less in cloudy weather and stop when it is very overcast. Store 2 to 3 days of water in your tank, or choose a hybrid AC/DC pump that switches to Eskom or a generator when needed.
Can I convert my existing borehole pump to solar?
Yes. A three-phase AC borehole pump can run on solar with a solar pump inverter (VFD) such as the EBH-3 range, which takes DC from the panels and drives the existing motor. Single-phase 220 V pumps usually need to be replaced with a solar or hybrid model.
Which way should my solar panels face?
In South Africa, face the panels north at a tilt of roughly 25 to 30 degrees and keep them out of shade from trees, buildings and the tank stand, especially between 9:00 and 15:00.
Shop solar pumps
Browse all solar pumps, solar borehole pumps and solar pump inverters, with delivery across South Africa. Need help? Call 012 881 1962 or WhatsApp 061 744 1001.