That 20K temperature difference will need some work. Maybe for hydronic floor heating or ceiling cooling under very mild conditions with excellent heat exchange

That 20K temperature difference will need some work. Maybe for hydronic floor heating or ceiling cooling under very mild conditions with excellent heat exchange on the exterior side, but for serious use, it’s not enough. So I guess the idea would be a multistage device? Very cool if it works and can be made without too many moving parts. I think that any really big reduction in refrigerant use will a side effect, though. Sure, modern A/C equipment has some refrigerant in it, but there is a lot of refrigerant in the often-fairly-long pipes between the indoor and outdoor equipment. Electrocaloric heaters (or gas-fired heat—and-hot-water devices or thermoacoustic devices or district heating or much any other fancy technology) will replace indoor refrigerant pipes with water pipes, which are messier if they leak but are otherwise quite environmentally friendly. This could be done today with no exotic tech at all. Just use an outdoor unit with a small sealed refrigerant system, perhaps using propane or CO2 or just less fluorocarbon or HFO refrigerant, and use indoor PEX water pipes to indoor fan coils. Some light regulation could nudge new construction in this direction. You can buy systems along these lines today. Bonus points for the fact that such a system could quite easily control the cooling coil temperature to adjust dehumidification rates.