I believe the Eight sleep uses a Peltier cooler. Not terribly efficient, but the ΔT and the load are low (a human body puts out <100W while asleep). Plus, a Pel

I believe the Eight sleep uses a Peltier cooler. Not terribly efficient, but the ΔT and the load are low (a human body puts out <100W while asleep). Plus, a Peltier can also heat with some supporting electronics.