Yeah, $300 summer utility bills make us want to cry every month, but not many pre-fab homes come with a built-in windmill and solar panels. You’re going to have to buy those separately, and even with tax credits a five kilowatt solar panel system will set you back $25,000, plus another $3,500 for a Tesla storage battery—plus whatever backup system you purchase, like a wind or water turbine, which can cost more than the solar panels. This isn’t even considering the cost of installing a well, rain barrels, and septic system, which Pure Energies estimates costs another $10,000.
Also, realize, you’re not just paying for electricity every month. You’re paying for engineers who design and repair the systems supplying the electricity. When it’s just you and your windmill out in the middle of Wyoming, you’re going to have to fix every breakdown yourself, or hire a specialty mechanic to drive out to your home, which can't be cheap.
When you’re growing your own food and generating your own power, you’re likely to be thriftier with electricity and waste—as long as you don’t drive those 100 miles to town very often. That composting toilet will probably help too.