I'm not an expert on hardware, but I do know that CPU consumption depends on CPU load. A laptop battery drains faster and fans run faster when the CPU is workin

I'm not an expert on hardware, but I do know that CPU consumption depends on CPU load. A laptop battery drains faster and fans run faster when the CPU is working than when it is idle. More MB/s mean less seconds and therefore more idle time. So how could running a program that has more instructions and takes longer to do the same work not have a cost? About the second part of your comment, it's true that optimizing has a cost, and if I were creating a "yes" or "cat" program for personal use it would obviously be pointless to optimize. But if it's a program ran by millions of people often (probably more true of "cat" than "yes"), it's not that obvious to me that millions of little savings cannot offset the time of one person optimizing.