The phrase "are significantly more efficient" is correct and usable in written English.
You can use it when comparing the efficiency of two or more items, processes, or systems, indicating a notable difference in their performance.
Example: "The new software updates are significantly more efficient than the previous versions, leading to faster processing times."
Alternatives: "are considerably more effective" or "are markedly more productive."
For example, in relation to building energy efficiency, the supermarkets have all developed "green stores", which are significantly more efficient than existing stores, and, in relation to transport, many of the retailers have worked with engine and vehicle manufacturers to test a range of new technologies.
Results show that the latter two are significantly more efficient than the former.
Diesel engines, which are significantly more efficient than petrol ones, produce less of the demon gas per unit of useful energy.
Few teams in the NBA are more trigger-friendly early in the shot clock from deep than Houston and Golden State, but, as shown below, the Warriors are significantly more efficient within that range.
Comparing the polarization curves shows that the two introduced tubular designs are significantly more efficient than the conventional, flat-shape PEMFC having the same active area.
Recent empirical research reveals that certain KA techniques are significantly more efficient than others in helping to extract certain types of knowledge within specific problem domains.
AMG is shown to be significantly more efficient than SGS.
His current prototype is significantly more efficient than the previous one, and closer to commercialization.
Both allelic-drive systems were significantly more efficient than a gene-drive CopyCat element inserted into the yellow locus.
This may not seem like a lot, but it is significantly more efficient than most other materials.
The major component in natural gas is methane, which is significantly more efficient at trapping heat — and warming the planet — than carbon dioxide.
