Benefits of Multi-Stage Furnaces

Single Stage Furnaces

Many older furnaces have only one stage of heat output and that is the maximum it can produce. This is great when the furnace kicks on first thing in the morning. Many people will use a programmable thermostat, which can be set for a specific temperature to be reached by a certain time, say 6:00 a.m. So for example, to go from a 65 degree setting to 70 or 72 degrees, it can take up to 30 minutes.

Once the temperature satisfies the thermostat setting, the furnace shuts off. So let’s say approximately 20 to 30 minutes later the temperature drops 2 degrees, the thermostat tells the furnace to come again. The furnace fires up at maximum, runs until it reaches the set temperature and then shuts off again. This maximum gas usage will continue to occur all day and into the evening.

Two-Stage Furnaces

To explain the two-stage furnace, I will use the same 6:00 a.m. scenario, where the temperature needs to be raised from 65 degrees to 70 or 72 degrees. A two-stage furnace will fire up at 50% of the heat output, using 50% of the gas usage. If it doesn’t satisfy the thermostat in about 5 to 7 minutes, the furnace will then kick up to maximum heat output.

Now here is where the money saving benefits of this type of furnace kicks in. Once the thermostat setting is satisfied, and as I mentioned before, 20 to 30 minutes later the temperature drops 2 degrees, the two-stage furnace works differently from the single-stage furnace to raise the temperature back to the thermostat setting. The two-stage will fire up at the low stage of 50% of the heat and use 50% of the gas usage. This is enough to raise the temperature back up to satisfy the thermostat. This process continues into the evening; the furnace is only using 50% of the gas it needs to satisfy the thermostat setting.

Do I see money being saved here big time!