[chadconway]

Zigbee is on the same frequency as WiFi and therefore suffers from all the same issues that WiFi has interference and limited range. SolarCity used Zigbee for communication with solar inverters. It was very unreliable. Tesla moved to WiFi after acquiring SolarCity.

[naasking]

Zigbee is sufficiently low bandwidth that interference is typically a non-issue, and repeaters for its mesh network are easy and cheap to add for extending range and dealing with interference. This simply isn't the case with WiFi.