Why are daily water requirements important to know, and not necessarily flow per hour?

Unlike conventional electric pumps which pump at a constant rate, once switched on, flow rates for solar pumps are variable over the course of the day. Therefore solar direct pumps start pumping slowly in the morning, with peak flow rate over midday, then dropping off in the afternoon.

Why is the borehole depth, and pump depth, of minor importance in solar submersible pump selection and sizing?

The important parameter is vertical lift which is NOT determined by the depth of the borehole, or the depth of the pump setting. It is determined by the depth of the water level in the borehole, plus lift ( height or elevation) above ground to the water delivery point.(see diagram)

Why are Solar Water Pumps not specified in Horsepower, Watts or Kilowatts?

Although solar pump motors and controllers have nominal power ratings, the power at which solar pumps operate are variable. This  depends on the solar array size,  and time of day ( sun radiation intensity varies over course of the day),  and factors such as temperature, pump geometry and dynamic head of  the application.

Are solar pumps cheaper than Diesel pumps?

Although the initial capital cost of diesel pumps may be lower than solar, the operating and maintenace cost for diesel accummulate quickly so that the break-even point for solar can be reached after a fairly short time, after which further savings accumulate, making solar a far cheaper option over the solar pump's life time.

To illustrate this, a Solar vs Diesel calculator is available which you can access by clicking on: Solar vs Diesel Calculator


Solar PV Panels


Solarworld SW245, 245Wp R3060.00 excl VAT
Solarworld SW180, 180Wp R2245.00 excl VAT
Solarworld SW145, 145Wp  R1810.00 excl VAT
Solarworld SW80, 80Wp R1020.00 excl VAT
Lorentz LC80, 80Wp R1060.00 excl VAT
Lorentz LC185, 185W R2220.00 excl VAT
Lorentz LC250, 250W R2870.00 excl VAT

Terms and Conditions apply – click here

Lorentz Solar Water Pumps

  • Submersible pumps to lift water from boreholes, dams and rivers for drinking water, irrigation applications etc
  • Surface pumps for swimming pool filtration & circulation, pond management, irrigation