The Little Brass Valve Wants the Crown

A trade publication marking its 100th year is running a bracket-style contest to name the greatest HVACR innovation of the past century, and the final matchup is set. The thermostatic expansion valve, or TXV, a small mechanical valve that controls refrigerant flow in air conditioners and heat pumps, won its semifinal with 74% of the vote, beating out low-GWP refrigerants (newer refrigerant blends designed to have less climate impact). It now faces inverter-driven compressors, which took 67% of the vote over ductless mini-splits to reach the final.

The matchup is a contrast in approaches to the same job: inverter-driven compressors let equipment ramp output up and down to match demand rather than running at one fixed speed, a feature that shows up in many modern high-efficiency heat pumps and air conditioners. The TXV is an older, simpler mechanical part that has quietly regulated refrigerant flow in cooling and heating systems for decades.

This is a reader vote for an industry anniversary poll, not a change to equipment, codes, or rebates. If you already own a system with an inverter-driven compressor or a TXV, nothing changes for your home. For homeowners, it is mostly a reminder of how much of today's heating and cooling technology, from the variable-speed compressors in newer heat pumps to the basic valves inside them, has been built up gradually over the past hundred years.