2. When you put your PC to sleep at night instead of turning it off, you save at least 25 minutes per month (in startup and shutdown time, I'm guessing), while spending only an extra five cents monthly.

I'm waiting to hear back from an Iolo rep on whether hibernate mode was considered in this study, as that would save you some startup/shutdown time and save you money as well.

(When your computer is in standby, it continues to draw a bit of power. In hibernate, however, it's effectively off.)

In any case, I think there's something to be said for pocketing an extra $24 annually just by putting your PC to sleep at night. And as someone who has long been annoyed by annoyingly long boot times, there's much to be said for resuming your work session almost immediately, right where you left off.