The HQRP 120V to 24V AC 20VA Transformer is a reliable replacement power supply compatible with Nest, Ecobee, Honeywell, and Sensi smart thermostats, as well as compatible with Ring video doorbells and other devices requiring constant 24V AC power. It delivers stable and consistent 24V AC output at 20VA, ensuring dependable operation of thermostats, doorbells, and smart home systems. Designed as a practical 120V-to-24V replacement transformer, this unit is compatible with Nest thermostats, Ecobee thermostats, Honeywell and Sensi systems, and compatible with Ring Video Doorbell, Ring Video Doorbell 2, Ring Video Doorbell Pro, Nest Skybell Doorbell, and other 24V-powered devices. It provides a dependable solution when the original transformer is insufficient, outdated, or needs replacement.