Sure, you can heat buildings, water etc. The miners who can mine bitcoin the most efficiently (i.e. monetise any wasted energy the best) will win and the others

Sure, you can heat buildings, water etc. The miners who can mine bitcoin the most efficiently (i.e. monetise any wasted energy the best) will win and the others will not be profitable and will go out of business. Miners are not location constrained like most energy users and are drawn to the cheapest energy sources around the world which tends to be otherwise wasted energy that no-one wants. If there's other demand for the energy it will be uneconomical for the miners to use, and they'll need to move elsewhere. Even if too many miners cluster in a certain location, their own demand will increase prices, forcing them to decentralise around the globe. So ultimately they end up spread around the world either using the energy no one wants and is otherwise wasted (i.e. ~free) or more expensive energy while efficiently monetising the by-products of mining (i.e. heat) They actually make otherwise unprofitable renewable energy sources, profitable, by offering a highly dynamic load that can monetise large amounts of unneeded (and unthrottlable) energy during periods of low demand (see the "duck curve"). Without this the solar farms etc could be unviable.