To the naysayers: these languages are either compiled, or will be JIT'ed at runtime. What they will be compiled to will be chip specific binaries-- x86, ARM, whatever. The energy usage will be markedly different depending on which chip architecture is chosen, and will no doubt be inconsistent between different architectures and languages.

Or to put it another way. Why do you think mobile devices almost exclusively use ARM? Why do datacenter operators invest heavily in R&D for ASICs instead of engineering new languages or runtimes? Because languages play a secondary role in energy consumption.

This study is just like countless of other meaningless benchmarks seen in language war flame posts. Pointless and misses the big picture.