High efficiency gas furnaces receive a rating between 90% and 96% by the American Society of Heating and Air Conditioning Engineers (ASHRAE). This rating is referred to as the annual fuel utilization efficiency, or the AFUE, and is a measure of seasonal performance.
Traditional “power combustion” furnaces have a rating between 80% and 82%. Furnaces that have ratings above 90% are “condensing” furnaces, meaning that they are able to condense escaping water vapor and consequently recapture some of the heat that is wasted by traditional furnaces.
Choosing a highly rated gas furnace will save you a lot of money and keep your home properly heated. Especially if you live in a colder climate, the American Council for an Energy-Efficient Economy (ACEEE) strongly recommends having a condensing furnace with an AFUE of 90% or higher.
One of the best choices of condensing furnaces is the Bryant Evolution Plus 90i series, which is also marketed as the Carrier WeatherMaker Infinity 96 series.
The Evolution series is Bryant’s top line. Bryant’s middle and bottom lines are Preferred and Legacy. The Evolution model has AFUE ratings between 94.1% and 96.6%. The Bryant Evolution Plus 90i has excellent heat/blower controls and according to the ACEEE, this furnace’s blower utilizes the smallest amount of electricity of any model, only 105 to 258 kilowatts per year.
With an AFUE rating of 95%, the Armstrong Air furnace is another great condensing model that is similar to the Bryant Evolution, but can cost you a couple of hundred dollars less.
There have been some reports, however, that have said both the Bryant and the Armstrong models need repairs more often than other furnace types and due to the high cost of parts, they can be difficult and expensive to repair. Even still, Bryant and Armstrong furnaces have average to above-average long-term reliability ratings.
Another highly efficient type of furnace is the multi-stage modulating gas furnace, whose AFUE rating is between 92% and 97%. This kind of furnace is a bit more expensive but both experts and homeowners agree that the multi-state modulating furnace yields the greatest level of comfort.
Two and three-stage furnaces have the ability to maintain a nearly constant temperature through the use of variable-speed blowers. A recommended brand name of a multi-stage furnace is the Rheem Prestige series, which has a modulating burner with a heat output range in 5% increments from 40% to 100%.
A gas furnace’s measurable performance is affected by climate changes, home size, insulation, window condition, and usage. As a result, long-term reliability is generally considered to be the most important distinguishing factor between furnaces, which are designed to last between 15 and 20 years. So while having a furnace with a reputable brand name is important, it is the relationship between the contractor and the buyer that is most often emphasized.
Originally posted 2010-03-20 00:19:25.