Daily Pumping Cost

Hi all, I am have designed a small CW system for treatment of greywater with a septic tank as pretreatment to settle out solids. I need to pump from the septic tank to the CW four times a day (for batch loading). I would appreciate some help in calculating the pumping cost. The outline is as follows:  Total head = 4.5 m  Q= 8m3/d  Pump consumption = 0.45 kWh Electricity cost= N$2 / kWH Pump + motor efficiency = unknown  Thanks in advance Megan