So I just ran the numbers and the majority of their expenses are on the insulation and construction, not the windows. I think it’s safe to assume they’re spending about $30,000 on insulation and thicker walls, that’s about $83 a month added to their mortgage over a traditional home. If you invested $83 a month in a high-yield mutual fund averaging 10% which really isn’t even that high and it’s over 30 years you’d have $172,000. The savings from not paying to heat your home barely breakeven especially since they’re “cheating” in this case by having solar panels. it sounds great and if you’re well to do you can get away with it but for most blue-collar folk they’re doing something to help the environment which is great but they’re spending well over $100,000 more just on insulation then they would’ve spent to heat the home. Some decent windows and some decent insulation is more than enough, I pay maybe $500 a month four months out of the year to heat a significantly larger house and I just leave the thermostat at 70f.