Monday, August 17, 2009
Will 2-stage furnace save me money?
Will a 2-stage gas furnace save me money?
Well this is kind of a loaded question. For example I am going to use a 95% efficient gas furnace. The brand does not matter. If you buy a Trane, Bryant, Carrier, Goodman, or Lennox there is not a measurable amount of difference. The bigger difference will be by what company installs it. Majority of furnaces installed are 1-stage. Which means when the house gets cold 100% of the heat comes on. The problem is if it isn't very cold out the furnace may only run for 5 or 10 minutes then shut off. A furnace needs to run at least 10 minutes before you can even get it up to 95% efficient. When if first comes on it will be maybe 50%, then 60%, and keep going up as it runs longer until it reaches peak efficiency. It is like a car, if you drive stop and go traffic your gas mileage is low, but if you go on the highway for 60 miles and don't stop your gas mileage goes up.
So if your furnace turns on and off to often you will not ever get to save money because the furnace doesn't get to peak efficiency. So back to the installing company. If they install a furnace that is to large for your home it will turn on and off to many times during the day cost you money and making your gas company lots of money. So a very common problem is if the installing company selects a furnace that is to large it will run on low stage to often wasting energy. So it is possible to put in a new more efficient furnace but have it not save you any money.
Today we have 1-stage, 2-stage, 3-stage, and modulating furnaces. The advantage of multi stage furnaces is better comfort in the home. If the furnace runs longer it will get the temperature more even in your rooms. Plus the longer the furnace runs and less on/off cycles reliability does go up. So multi stage may help the furnace last longer which will save you money. But you may not be saving what you should be. Depending on model's the first stage (low heat) could be only 70-85% efficient, compared to high heat when it could be 95% efficient. A properly installed 1-stage or multi stage furnace will give you far better long term results. As time goes on gas will keep going up. A well installed furnace could last your 15-20 years. So why over pay each month on your gas bill. Be very careful on selecting your installing contractor because that can save you $1,000's of dollars over the next 15-20 years.
So the moral of the story is "just because your new furnace is 2-STAGE, that does not mean it will save you more money".