Works with most single-stage heating and cooling systems. Compatible with single-stage standard heating and cooling, standard central heating only, standard central cooling only, furnace, gas fireplace (24 volt), millivolt heating, hydronic (hot water or steam) heating-2 wires, and heat pump (without auxiliary heat). Easy to install and use, mounting hardware and installation guide included. Durable construction, mercury free. Operates with batteries or hard-wire configurations. Requires 2 AA alkaline batteries (not included). 3 years warranty.