An interconnected wireless HVAC (heating, ventilation, air conditioning) system and wireless security system, which are interconnected and communicate with each other through the use of a common wireless technology, including the same selected frequency, modulation and a set of common protocols. The Wireless HVAC system includes wireless thermostats, which can communicate with and control both the HVAC system and the security system, and the wireless security system includes wireless controls or keypads, which can communicate with and control both the security system and the HVAC system. The universal wireless infrastructure can be expanded to provide communication or control of additional user or manufacturer installed wireless devices or systems through the universal wireless home infrastructure.