Wow, I never cease to be amazed at how few of the HN comments have anything to do with the original post. I guess I'll jump on the bandwagon, while my comment

Wow, I never cease to be amazed at how few of the HN comments have anything to do with the original post. I guess I'll jump on the bandwagon, while my comment is tangential, it does have to do with the article's focus on reducing greenhouse gases and fuel consumption. Switching to a heat pump should be done in all cases where a traditional A/C is being replaced, but the biggest bang for the buck is in how the house is constructed in the first place. "Passive solar" orientation and insulation can prevent a HUGE amount of energy consumption. To point to another HN post article: https://thebaffler.com/salvos/construction-time-again-sisson https://thebaffler.com/salvos/construction-time-again-sisson I've been saying for 20 years here in San Diego county, that if developers built track housing with passive solar orientation, and covered them with photovoltaic, the neighborhoods would be power plants. They could offer free HOAs and free electricity for the life of the house. Instead, we orient, organize and build for the maximum efficiency of a group of people who are only onsite for about 1 year (the developers) and then leave the people who live there for decades holding the bag.