As others have pointed out there are still non-btc crypto-currencies that are worth GPU or even CPU mining[1]. But they don't even have to be making a raw prof

As others have pointed out there are still non-btc crypto-currencies that are worth GPU or even CPU mining[1]. But they don't even have to be making a raw profit vs the electricity they are consuming. If, as you say, the spare capacity must be kept warm anyway, then they only need to be profitable vs the delta of electricity consumption between idle and fans blowing 100%. So whatever capacity is left beyond the fixed and spot market _could_ still be earning them something. [1] http://cryptomining-blog.com/6090-crypto-coins-to-check-out-for-cpu-mining/ http://cryptomining-blog.com/6090-crypto-coins-to-check-out-... Edit: fixed spelling.