Furance gas consumption.....single stage heat vs multistage

[im4snow2000]

Had a discussion recently with collegues about the consumer's real benefit between a furnace with a single stage gas valve vs a multi-stage or modulating gas valve.

One school of thought says the net fuel consumption is similar between the furnaces as the multistage will run longer, since it's BTU delivery on low fire is less than the single stage. Thus, the real benefit to a consumer from a multi-stage gas valve is the temperature balance.

Thoughts on this?

[chambery1]

I agree.

Therefore, the question is "What price to pay for that comfort?"

[Au-en-boy]

If the AFUE is the same for both furnaces, no amount of staging or modulating will save your homeowner any money on the gas bill. The only thing that will affect the fuel bill is the efficiency of the furnace. Staging or modulation will make the home more comfortable, though..... better for sitting on the couch drinking beer! :couch:

[amd]

A multi-stage furnace can save energy if it allows for a use of a lower setpoint.

[Junkers]

With a multistage or variable blower there will be better humidity control as well. Also, fewer start/stop cycles will result in somewhat longer durability of the unit and a somewhat lower energy consumption due to the fewer warm-up, cool-down fan use. Finally, the variable speed fan uses an ECM motor that would use at least 25% less energy during normal use and far more if the fan is used continuously.