Centrifugal pumps are the most common types of the pumps used in the agriculture fields. If they are of proper size, design and of good material then they may lead to high efficiencies . In Pakistan most of far mers use pumps which are less energy efficient . The issue of less energy efficiency in tube wells is mainly due to mismatch of motor power with the size of impeller. Due to high energy requirements the most commonly used centrifugal pumps are working far away from their best efficiency point (BEP) and impart extra economic burden on the farmers . Now it is the time to study the pumps properly and adopt potential energy saving opportunities like “Impeller trimming”. Whereas trimming of impellers is common practice that is used to adjust pump characteristics like flow rate and head to actual requirements. In this study it was tried to compare the “Energy Efficiency” of local made centrifugal pumps. Pump cha racteristics curves of different sized centrifugal pumps and same pump with different impeller diameters were drawn to compare them . A centrifugal Pump having size (100 mm× 125 mm) was tested with impeller diameters (222, 212, 195 and 180 mm). Pump showed discharges ( 42.64 lps, 8.81 lps, 36.79 lps and 31.19 lps) and power requirements (16.6 Amp, 14.6Amp, 10.8 Amp and 8.5 Amp) respectively. From above it was found that the reduction in discharge was 11.45 lps (27 %) which was less as compare to reduction i n power requir ement 8.1 Amp (49 %) as we reduced the impeller diameter from 222mm to 180 mm. Similarly it was observed that large sized pump (125 mm×150 mm having efficiency 76.48 %) were more effi cient as compared to small pump (63 mm×75 mm having efficiency 63.18 %).
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