My computer is on 24/7 regardless, and while the mining will use abit of extra power.
It will not be anything substantial. That's all I have to think about regarding it.
Hmm - I guess your mining very low Mh/s or CPU mining.
GPU mining makes you power usage jump dramatically above non-mining levels with useful Mh/s values ...
this is correct. Not mining I use maybe 80W, mining it goes up to 380W. This is 2x5870s