The phrase "actually more efficient than" is correct and usable in written English.
You can use it when comparing the efficiency of two or more things, indicating that one is more efficient than another in a specific context.
Example: "After conducting several tests, we found that the new software is actually more efficient than the previous version."
Alternatives: "truly more effective than" or "genuinely more efficient than".
Even though those solutions are actually more efficient than RSTP, they are more expensive.
Oddly enough, reading traditional print media is actually more efficient than this, because the story is mentioned only once per paper.
Although (k_{CS,3} > k_{CS,4}), node 4 is actually more efficient than node 3 in terms of integrating neighbor resources, because, according to Eq. 8, (c_{NCSC,4} = 1 > c_{NCSC,3} = 0.75).
Two hours later, and Sainsbury was still to be found locked in intense conversation about whether Agas are actually more efficient than modern cookers.
(In a letter sent to shareholders on Tuesday, Netflix said that its original programming last year was actually more "efficient" than "most of" its licensed content. This means in 2014, it actually cost Netflix less to produce original content than to license some content from other studios, in terms of how much of it people watch).
Indeed, calcein-F efflux from mitochondria was actually more efficient than that from the whole cells.
A post hoc analysis did show, to our surprise, that irrelevant action cues were actually more efficient at eliciting dynamic gestures than were task-relevant cues, in that a higher proportion of the total gestures that were produced were dynamic.
If you are leaving the room for less than 15 minutes, it is actually more efficient to keep a CFL on for that time.
ULR was actually systematically more efficient than CLR.
Interestingly, we also found that an optimized AP approach actually was more efficient than MM/PBSA contrary to common belief [17].
Moreover, the electric power actually delivered to the EV is much more efficient than the crude oil to refinery to gas station to gas tank to heat-producing internal combustion engine.
