How do I measure pump efficiency using BAS data?

Pump efficiency (wire-to-water efficiency) calculation requires three real-time measurements: pump differential pressure (ΔP in PSI or ft of head), pump flow rate (GPM), and pump motor power (kW). The hydraulic power is calculated as (ΔP × flow) / constant, and the wire-to-water efficiency = hydraulic power / electrical power × 100%. In a BAS, the pump ΔP can be measured directly with a DP transmitter across the pump suction and discharge, flow is measured via an inline or insertion flow meter (electromagnetic or ultrasonic), and pump kW should ideally come from a Modbus-connected VFD or power meter rather than proxy measurements. Per ASHRAE Guideline 22, pump efficiency below 65–70% indicates a problem with impeller wear, pump oversizing, or excessive throttling. Modern analytics platforms can trend the pump efficiency curve over time and detect degradation before it impacts system performance — Belimo Energy Valves with their built-in flow and temperature sensing combined with DP transmitters can calculate coil-level and branch efficiency without dedicated pump instrumentation.