Why does the eco-friendliness of the processor you're testing on matter at all? I can guarantee you that your users are not going to go out and purchase less power-efficient CPUs themselves just because you tested on a power-inefficient CPU yourself.
And, the amount of electricity that you, the developer, spend testing your code will almost always be eclipsed by that of your users if more than a dozen others use your tool.
So, again: why does it matter how power-efficient the CPU you're testing on is, as long as it's slow (to produce the proper throttling effect)?
I was alluding to replacing the idea of holding on to a Pentium 4 with buying a modern, more eco-friendly, but ultimately just as anemic, CPU.
Not a perfectly representative test, sure, I just felt that it was a good compromise between "test your code on weak machines" and "be environmentally responsible".
So yep, I did conflate weak CPU with low-wattage CPU, you are right.
And, the amount of electricity that you, the developer, spend testing your code will almost always be eclipsed by that of your users if more than a dozen others use your tool.
So, again: why does it matter how power-efficient the CPU you're testing on is, as long as it's slow (to produce the proper throttling effect)?