They are standard outdoor air heat exchangers so below about 35F efficiency drops significantly. That's pretty rare around here so it is almost always enough - we can still gain about 45F vs the outdoor temperature even below 20F.

We don't have natural gas available where I live, only propane. When I purchased the heat pumps, propane was $5/gallon for 91,500 BTU. That translates to about $4.60/hr to run 84,000 BTU/hr of furnace. With electric energy (cheap in Texas!) at about $0.11/KWh, the equivalent costs of my heat pumps was and remains close to about $0.55/hr to run.

In the summer, they cool with equal capacity and similar power consumption for a 15 SEER rating (waste heat from the system components works against cooling in the summer!)

Factor in your acquisition costs (mine, just after the housing bust and with a little legwork, were about 20% of retail at the time, so a no-brainer) and you can get a lot more objective idea what you're really accomplishing.

https://www.hotwater.com/info-center/doe-regulations/doe-res...

Electricity prices might come down over time (renewables push down generation costs), natural gas prices won’t due to global demand for it.

In this configuration a typical suburban home can provide ALL of it's own energy needs, including 2 electric cars.

This also needs to come along with a massive reorganization of the US' electric utilities, which are primarily optimized to provide the most money possible to some rich assholes.

Instead we should be optimized for local generation, storage and distribution.

That is to say, we should be technologically optimized, not shareholder return optimized.

Obviously, this won't happen while the world's richest have the sway that they currently hold on policy.

But in the mean time, each homeowner can move ahead with local generation and storage that provides for all of their local energy consumption.

And YES, it does pay for itself over a shorter time span than a typical mortgage...