Nest and Ecobee can work with many common 24V heating and cooling systems, including some heat pumps

https://writehollow.com/s/TWb5Qirrr0OZ7g0Y7LOaA

Nest and Ecobee can work with many common 24V heating and cooling systems, including some heat pumps, though certain homes may need a C-wire or add-on power accessory.