The heat from your computer is not wasted if you need to heat your home. If you're using electric heat where you live, then your computer's heat isn't a waste. It's equal cost if you generate the heat with your computer.
If you have other cheaper heating than electric, then the waste is only the difference in cost.
If it's summer and you're using A/C, then it's twice.
Bitcoin generation should end up where it's cheapest. Maybe that will be in cold climates where there's electric heat, where it would be essentially free.