It's a $300 part that allows swapping the direction of heat flow. This tiny upfront cost is enough to block tons of good practice. Nate the House Whisperer is

It's a $300 part that allows swapping the direction of heat flow. This tiny upfront cost is enough to block tons of good practice. Nate the House Whisperer is a guy who has been trying to build a new generation of HVAC practice, and though he says he's usually a libertarian, he advocates for adding a tax to AC-only units that would eliminate this price difference (or some similar practice, I forget the exact details...)