Could you explain your comment more? The way I understand it is:

- I have two servers with the exact same hardware - one runs a Ruby on Rails web app - the other runs a Vert.X web app - both apps have similar features to the end users - if I run both of them for a month, the server running the Ruby on Rails app will consume hundred times more energy in kWh compared to the server with the Vert.X app - another way to look at it, to serve the same number of visitors, I would need hundred servers running a Ruby on Rails apps and one server running a Vert.X app

Is that correct?

It hasn't been my experience when I measured the long-term consumptions with energy meters in real-life scenarios. How did you arrive at your number?

By comparison, going from resistive heating to a heat pump is a 2.5x-4x jump in efficiency. 100x gains would be nothing short of spectacular.

I noticed the best energy savings when switching to Arm CPUs, but that's a separate topic.