Single Stage (Traditional Gas Heat and Electric AC Systems)

Single-stage heating means the furnace has one level of heat output. An example would be if you only have a gas or forced air heater or if you have an electric AC system and then a separate heating system. This is the most common type of system and are common all over the country. Generally 6 wires or less are used here.

Multi Stage Heat Pump

Two-stage heating means the furnace has two levels of heat output: high for cold, winter days and low for milder days. Since the low setting is adequate for meeting household cooling demands 80% of the time, a two-stge unit runs for longer periods and provides more even heat distribution. A heat pump is a single system that heats and cools. If you have a heat pump you will not have a separate air conditioning system. A multi-stage heat pump has an emergency or auxiliary heat setting for especially cold days. These systems are popular all over the country, but especially in the Northeast. Generally more than five wires are used and almost always with a W2 and a C or X wire.

Line Voltage Electric Heat

These systems use direct current instead of only 24 volts. The power wires are thicker and generally run either with 120 or 240 volts. Line voltage electric heat thermostats are common in older constructions--especially with baseboard heaters and electric heaters. These are NOT to be used with gas heating systems(gas heaters are generally single stage systems). Most line voltage systems are mechanical rather than digital programmable, and are almost always either 2 or 4 wires.

Unsure or System Not Listed?

Use this option if you are unsure of the type of thermostat system you need, or if you know your type of system and it is not listed.