Hi Megan, the basic ...

Hi Megan,

the basic equation to determine the power required to pump is P = QWH / e where P is power in KW, Q is your flow rate in m3/s, W = weight of water = 1000 kg/m3 x gravity = 9.81, H = head to pump which comprises the static head that you can measure plus the friction head which you calculate from the flow rate and pipe type and diameter.  e is the efficiency of the pump and motor which you could estimate initially as 50%.  Although your pump is rated at 0.45 kW, it will probably operate at a lower power consumption which you will determine as above.  Making some assumptions - pump for 1 hour 4 times per day gives Q=2m3/h, static head = 4.5m and friction head for 20m length of a 40mm HDPE pipe = 0.12m hence total head = 4.62m.  In this case P = 2/3600 x 1000 x 9.81 x 4.62 / 0.5 = 50 W or 0.05 kW.  So with these assumptions your pumping cost per day would amount to 4 x 0.05 x N$2 = N$0.4 per day or N$12 per month.