> but that same technology is rare in installed central HVACs, because the licensing and certification requirements impede the adaptation of newer more-efficien

> but that same technology is rare in installed central HVACs, because the licensing and certification requirements impede the adaptation of newer more-efficient technology, despite the requirements ostensibly existing to increase its use, but in practice providing protectionism at the expense of modern efficient technology. In practice, the single stage condensing units tend to be significantly more reliable. Inverter units require specialized control boards and semiconductors. The most advanced piece of logic in my condensing unit is a macro-scale electromagnet that keeps a circuit closed. I have several replacements sitting around my garage somewhere in a box. These components are brand agnostic so I could probably help my neighbors out too (or vice versa). A single stage condenser can often survive things like a direct lightning strike. Also, if you live in a place like Texas gulf coast region, there isn't really a point to having a speed lower than 100%. You'd have 2-3 weeks out of the year where that would actually be useful.