Trying to measure programming languages based on how much electricity they use is a lot like ranking aircrafts by their weight - completely meaningless metric.
If Erlang was so slow, it wouldn't be running WhatsApp.
If C is so efficient then no programming languages would have been created since 1970s.
Lua was designed to be tiny and easy to embed.
- Easy to write. - Easy to upgrade and modify.
If Lua was geared towards performance it would look a lot like C++ or Rust - thank God it doesn't .
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Also the biggest consumers of electric power are humans, by that logic Java would be at the bottom due to the sheer biomass of people writing it.
Programmer time is worth a lot more than CPU time, that should be the biggest thing people concentrate on optimizing.
Also I using Lua for Solar Energy, in theory Lua is creating electricity !!