If you're using the waste heat to heat your house, you should consider the difference in cost between heating with electricity versus whatever hydrocarbon you would normally use, and include the profit from mining. Its more likely than not you'll find the 11.5 cents per KWH profitability is much lower by offsetting your heating costs and the higher profitability of mining alts with GPUs. Your profitability per KWH might even be negative (meaning you're stupid if you don't do it). You could also use mining to 'store' excess solar power generation, and use the heat for your house. If you really get sophisticated, you could use waste heat from your mining equipment to preheat your domestic water when you don't need to heat your house. As far as mining altcoins, I don't see that as immoral any more than selling diamonds or gold is immoral. I personally have no use for those things, but someone does so long as you can sell it.