How Energy Efficient Is My Gas Furnace?
The concept of the “high-efficiency furnace” dates back to the 1980s when the National Appliance Energy Conservation Act of 1987 required all new furnaces be at least 78 percent efficient, meaning 78 percent of the heat stays inside the home. Before then, up to percent of a furnace’s heat escaped outside through the vent. Today’s standard furnaces are 80 percent efficient, while those with a rating of 90 percent or more are considered high-efficiency.
Here’s an overview of what a furnace efficiency rating is, why it’s important, and how you can determine yours.
What Is a Furnace Energy Efficiency Rating?
Because all furnaces that generate heat with a flame produce carbon monoxide, they need to be vented. It’s through these vents that some heat inevitably escapes. Furnace 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
It’s important to note that AFUE primarily tracks heat lost via intentional venting. It does not factor in heat loss due to gaps in the duct system, poor insulation, and other air leaks. So, if you have a super-efficient furnace but no insulation in the walls or leaky ductwork, your heating bill will likely be sky-high.
It’s also 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 Furnace
All furnace manufacturers are required to display the AFUE, typically found on a bright yellow label on the outside of the unit. If the label is missing or damaged, you can look up the model number online to learn the AFUE. You can also 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 through a metal flue, it’s a standard efficiency unit.
- If it has a pair of PVC pipes acting as draw and vent, that’s a sign of sealed combustion, meaning it’s a high-efficiency furnace.
Energy Efficiency and Cost
High efficiency furnaces cost more upfront but save on energy consumption in the long run. So the question is, do the energy savings justify the higher initial purchase price? That depends on several factors, including how your home is designed and insulated, how often you use your furnace, and how long you plan to stay in your current home. The final cost of furnace installation will depend on the size and layout of your home, the make, model and features of the furnace, and whether new venting is required to accommodate the sealed combustion system of a high-efficiency system. As mentioned previously, a drafty, poorly insulated home will likely not reap the benefits of a high-efficiency furnace. While determining a furnace’s efficiency is an important first step, it’s only part of evaluating your home’s overall energy consumption.
If your heating system has finally given up or you’ve decided to replace it before it does, we’re here to help. Contact us today for a thorough analysis of your home comfort needs and a new system proposal.
