Establish the actual duty-point path

Request supported curves at the proposed speeds and the system's static and friction components. Identify where each speed operates, rather than scaling the original flow and power independently. The permitted pumping region and source conditions still apply. A convenient cube-law calculation can conceal a point with poor efficiency, insufficient head or an unacceptable operating condition.

Compare energy per accepted delivery

Hypothetically, one supported schedule delivers 20 cubic metres using 8 kWh, or 0.4 kWh per cubic metre. Another delivers the same volume using 7 kWh, or 0.35 kWh per cubic metre. The reduction is 1 kWh for that service. These invented values are not pump data. A lower instantaneous kW does not establish that result if the longer run consumes more total energy.

Retain the operating hours used to deliver the comparison volume. Reporting only lower kW can conceal that the apparently efficient alternative requires a longer period that is unavailable within the service deadline.

Combine efficiency and wind matching carefully

A schedule can increase direct wind consumption while reducing hydraulic efficiency, or improve efficiency while accepting less surplus. Report both effects separately. Include a realistic completion deadline and actual permissible speed changes. Ask the wind integrator to assess the accepted electrical trajectory, while the pump specialist approves the duty points. Grundfos curve information supports the need for matched conditions; it does not validate a particular MARSTON interface or prove a universal percentage saving from reducing speed.