Efficiency test for motor drives
To determine efficiency, you need to load the controller appropriately and then measure the input and output power or the losses. Neither of those is easy to do accurately. Wattmeters that can measure the power accurately may be quite expensive. You may find it easier to enclose the controller in an insulated box and measure the temperature rise of air flowing through the box to remove the heat. You will need to control and measure the air flow. You will also need to know the humidity and barometric pressure.

You may be able to determine the losses by simulation as accurately as you can measure them.