Your comments about solar water heaters are irrelevant, because people aren't buying them (in the dominant markets). They are therefore inferior in some way (don't work particularly well in built-up cities for example, which is where populations are moving), in the opinion of the people making the purchases. That's the only opinion that matters, not yours.
Solar water heaters have issues. And mining doesn't
You're not getting that nobody is proposing "mining" in anything like the form it is done today, with all of its issues. Embedded deeply into a product (or indeed embedded deeply into a chip which is embedded deeply into a product) it won't be recognizable.
for the first time ever in Bitcoin's history, we'll have a scalable mining ASIC embedded in the most popular portable computing device on the planet (smartphones) whose growth is set to skyrocket and turn billions of unbanked into banked clients not only for micropayments but for standard commerce via a hardware wallet. the portability aspect of this device potentially will allow it to mine for free. right now i can envision unemployed African kids camped out at Starbucks or public libraries with not one but 7 Android phones (2 in their front pockets, 2 in their back pockets, 2 in their shirt pockets, and 1 in their hands for surfing) plugged into public outlets generating BTC while they're sipping their lattes. wait, nevermind Starbucks. why not go to the airports where it's plain to see the proliferation of phone charging kiosks in preparation for the smartphone age?
free electricity for all!