The two platforms share impellers and housings; the difference is the motor and how it is controlled.
Efficiency and part load
An EC (electronically commutated) motor is a permanent-magnet brushless DC motor with integrated electronics fed from AC mains. Motor efficiency is high across the speed range, whereas an AC external-rotor motor is efficient only near its rated speed. In HVAC applications that run at part load most of the time, this translates into roughly 30% lower energy consumption; under strongly variable duty the difference is larger. Always confirm against the actual load profile.
Control
EC fans accept a 0–10 V or PWM signal and report speed or fault status, so they integrate with building management systems and can be run as fan walls with redundancy. AC fans are fixed speed or step-controlled by voltage taps; speed control by phase cutting is possible but noisy and limited.
Cost
EC fans cost more per unit. The premium pays back through electricity savings, typically within 1–3 years at commercial run hours, and through reduced control hardware (no external drive or contactors). For constant-duty applications with few run hours, AC remains the economical choice.
Same duty point, both platforms
Use the selector with the motor filter set to EC and AC in turn: the results list the input power at the nameplate for both, so the energy difference at your duty point can be estimated directly.