The below article references a study of the energy efficiency of various languages. Fortran is listed as requiring more than 2.5 times the energy of C. It says the programs used are taken from a popular set of benchmark problems (The Computer Language Benchmarks Game - Wikipedia). Perhaps for those of you who are interested this would be another great place to submit improvements to the Fortran solutions.
I was just reading the same article. The web page from the authors is this one: Original work in SLE'17
On one of the benchmarks, Fortran was most energy efficient.