Mag Drive 18 Pump - low wattage?

[bigsteeviestyle]

I bought a used 180G set up. The included pump is a mag drive 18B. According to everything I can find, this pump should be pulling 150 watts. When I plugged the pump into a kill-a-watt, the reported usage fluctuates between 89 and 90 watts. I haven't tested to see if the pump is moving as much water as would be expected. What could be causing this and should I be concerned?

[degibson84]

I read somewhere that mag drives run out lower wattage at higher head height

[badguitarist]

they also run at lower wattage if they are throttled back, as in a valve on the outflow.

[Aslmx]

The wattage on the device is usually an over estimate as well

[Wazzel]

The rating is max draw and happens during start up. Operating is going to be less.