If your furnace is old or needing major repairs, now is the time to think about a new one before the snow flies.
In 1987 an act was passed stating that furnaces had to be 78% efficient, meaning that 78% of the heat had to go into the home. Prior to that, some furnaces let 40% of the heat go outside through the vent.
Today we have standard furnaces that are 80 percent efficient and some that are 90% or more and the 90% or more are considered high-efficiency.
What Do Furnace Energy Efficiency Ratings Mean?
All furnaces that generate heat with a flame produce carbon monoxide. Venting this gas allows some heat to escape. Efficiency is defined as the annual heat output of the furnace divided by the annual energy it consumes. This ratio is called the Average Fuel Utilization Efficiency (AFUE).
Understanding Furnace Energy Efficiency Ratings
We will be talking about gas furnaces and boilers. Fully electric furnaces do not lose any heat through venting gas, so they are all considered high-efficiency.
A heat pump is not the same as an electric furnace. Heat pumps have exterior units and use a separate measure of efficiency. However, most heat pumps have a back-up heat source, usually a gas or electric furnace, and that furnace will have an AFUE rating.
AFUE primarily tracks heat lost through intentional venting. It doesn’t factor in heat loss due to gaps in the duct system or poor insulation. A furnace or boiler’s efficiency is only one part of the heating equation. If you have a hyper-efficient furnace but no insulation in the walls, your heating bill will still be sky-high.
It’s important to understand that efficiency isn’t the only factor that determines operating cost. A low-efficiency furnace equipped with a variable speed blower or two-stage heating may consume less energy overall than a high-efficiency furnace running at full power.
How to Determine If You Have a High-Efficiency Heating System
Manufacturers are required to display the AFUE on boilers and furnaces. There will be a bright yellow label on the outside of the furnace. It should display the AFUE and indicate whether it’s high efficiency or not. If the label is missing or damaged, you can look up the model number online to learn the AFUE. You can also simply look at the layout of the furnace to determine if it’s high efficiency. Here’s how:
If the furnace vents to the chimney or roof via a metal flue, then it’s standard efficiency. If the furnace has a pair of PVC pipes acting as draw and vent, that’s a sign of sealed combustion, meaning that it’s high-efficiency.
High efficiency furnaces cost more but they save on energy consumption. The question is, are the savings enough to justify the higher initial purchase cost? The answer depends on how your home is designed and insulated, how much you use your furnace, and how long you plan to be in your home.
The final cost of a furnace install will depend on the size and layout of your home, as well as the make, model and features of the furnace. In general, most manufacturers price their high-efficiency furnaces at one-and-a-half to two times the cost of a standard-efficiency model. That could be anywhere from $2,000 to $6,000.
In addition, installing a home’s first high-efficiency furnace or boiler will mean extra cost, since the sealed-combustion system will require new venting (the dual PVC pipe system). Depending on your home’s layout, this may be a minor expense or a major headache. It may also require you to rework the ventilation for a gas water heater. Every home is different, but It’s reasonable to figure in a few hundred dollars here.
There may also be tax implications that affect your cost. These change based when regulations are passed, extended or repealed. So check the latest information from an official source, such as the DOE’s Energy Star site.
Determining a furnace’s efficiency is an important first step, but it’s only part of evaluating your home’s overall energy consumption.