[rsynnott]

There's no metric for that that's well understood by the public, though. People have been trained that more watts == more better over the last century by lightbulbs and things (and more dubiously by hifi makers; they tend to use very dubious marketing watts). Air watts (ie power of air movement) might have been a good compromise; most super-high wattage machines don't have substantially better air watts metrics. It still isn't that helpful to the consumer, though; a poorly designed machine may have high air watts but limited suction.

[silvestrov]

People can be taught.

Example of typical packaging of LED bulb in Denmark: https://imgur.com/a/J5PiGLb

It has: actual watt usage, "old watt equivalent" and lumen. It won't take that many years before people know the lumen value they want.

[nitrogen]

Inches of water column were directly demonstrated by the last door to door vacuum sales pitch I saw, as a measure of suction. CFM are a perfectly comparable measure of airflow. And an abstract "cleaning power" could be defined for various surfaces by putting a standardized dirt load on the surface and weighing what percentage remains after a standardized sweep.