It's probably not a great comparison to compare the theoretical numbers of Frontier to the achieved numbers of the green 500. The achieved flops is pretty much always considerably lower than the theoretical flops. Titan is a 27 PFLOPS machine that achieves 17.6 PFLOPS, sequoia is a 20 PFLOPS machine that achieves 17, summit is a 200 PFLOPS machine that achieves 143, ...

~ 37 GFLOPS/W is probably a better projection if we assume (out of nowhere) that the theoretical/achieved ratio of Frontier is comparable to Summit (75%). Still very impressive.