Of course you realize I'm proposing new houses, not retrofit. When I bought my house in Winnipeg in 1990, purchase price was $46,500. When I moved in, one neighbour laughed. She said the previous owner paid $36,000, and the one before that paid $24,000. Today the city assessment property tax is $102,000, and this is a tiny house built in 1907. A typical Winnipeg bungalow today is a quarter million. As an example:
a new house in a new housing division, 2 story with double attached garage, 3 bedroom, 1778 square feet, 42'x118' lot, list price is $479,00. At that extreme, the house should be descent. So why not install DC wiring and DC appliances for new houses? It doesn't require custom power cables, existing AC cables can be used for DC. Just ensure AC appliances aren't plugged into cables carrying DC power.
CFL bulbs run on 12V & 24V DC