... electricity cost ... assuming you aren't having to constantly heat your reef....
That selected part of the quote is really key for pumps and powerheads.
The bay area is cool. Except for a few weeks in the summer, most of us do not use chillers, and have
electric heaters running at some point during the day.
So power efficiency of anything
fully submerged simply does not matter.
Wasted power gets turned into heat, so heater runs less.
Ironically, devices like Abyzz have external power supplies and controls.
While more efficient, that heat is OUTSIDE the tank, so is wasted.
Thus, your old crappy mag drive pumps are "overall" more efficient than Abyzz.
Especially true of Vortechs.
Of course, taken to the extreme, it will put too much heat in your tank, bumping you to the point
of needing a chiller, which of course really wastes power.