That would be cool. The power supply specific inefficiency loss will likely only be measurable on the DC side of the power supply. The conversion from AC to DC is where the inefficiencies lay and the Killawatt won’t be able to capture only the power supply inefficiency. Rather you’d be measuring a combination of the two, the PPE shift + power supply inefficiency. Either way, it would be neat to see your results. You should be able to look up the specs online for whatever the power supply is on your fixture.
Also FYI, here’s an example what happens when a fixture heats-up (from a Fluence unit we’d measured):
