Reducing Impeller Size for Oversized Pump to Reduce Energy Consumption by 25 PercentÂ
Analysis of the pump was showed the pressure generated was considerably higher than required. Reducing the impeller size was explored which reduced the power demand by 25 percent. Fitting an alternative motor to the pump allowed more energy consumption reductions.
Category: Blogs, Case Studies November 1, 2025
Intended Audience: All pump users.
Objective: Consider alternatives to a pump that is generating more pressure than necessary to reduce costs of operation.
Description of System: Operational analysis showed that the pressure generated by the pump was considerably higher than necessary. After discussing the results with the pump manufacturer, it was found possible to reduce the impeller diameter.
The original duty was 230m3/hr (1010 USgpm) at 112 m (367 ft) head with a 2960 rpm 110 kW (150 hp) induction motor.
Description of Intervention: The impeller could be reduced from 320 mm to 280 mm, which would reduce the power demand by more than 25 percent (power absorbed is proportional to the ratio of diameters to the third power). The annual energy demand fell by 83 MWh.
In a secondary investigation, it was found that by fitting a 75 kW (100 hp) motor running near to its peak efficiency, the annual energy consumption could be reduced by an additional 16 MWh (7 percent).
The previous instability of the system meant that around 4500 Euro was spent annually on maintenance of the pump, valve, and pipeline. This was eliminated by cutting excess flow.
See Table 1 below:
Table 1: Summary of Results
Summary of Results: In addition to the saved energy and maintenance costs and improved system stability, cavitation in the throttling valve was reduced and excessive vibration and unacceptable noise eliminated. See Table 1 below for specifics.
Conclusion: This cost-saving opportunity is very widespread. This is because pumps are frequently oversized when it is difficult to calculate the system losses. The pump manufacturer should be consulted, but in most cases, it is possible to reduce the impeller at very little cost.
Written by:
Members of the Committee, 1st Edition
Published In: Pump Life Cycle Cost: A Guide to LCC Analysis for Pumping Systems, 2nd Edition
Year of Publication: 2021
Pump Life Cycle Costs: A Guide to LCC Analysis for Pumping Systems – 2nd Edition – Pumps.org
SUBSCRIBE TODAY
Get the latest pump industry news, insights, and analysis delivered to your inbox.