you don’t know his actual usage

Why would I need to know his usage? Whatever it might be, a newer CPU can do the same amount of work as an old CPU for a fraction of the energy.

meaningless anyway unless you subtract from it the energy use from manufacturing and distributing a new system, as well as that from disposing of the old one.

You mean the CPU that was already manufactured years ago and won’t magically disappear due to you refusing to upgrade to it? Whether you use it or not the energy to create it was already spent.

you haven’t addressed the other problems mentioned at all

And I didn’t mean to. I simply corrected you when you congratulated him for using less energy, which is not true.