You may have seen the term “high-efficiency” used to describe a furnace or boiler, but how is efficiency actually measured? The answer is Annual Fuel Utilization Efficiency, or AFUE (pronounced “a-few”). AFUE is a measure of how efficiently heating equipment converts the energy in its fuel to heat over the span of a year. It’s the annual ratio of heat output compared to the total annual fossil fuel energy consumed.
As an example, a boiler boasting a 95 percent AFUE rating converts 95 percent of the energy in its fuel to useful heat for the home, while the remaining 5 percent escapes through the chimney, walls, windows, doors and elsewhere. Energy.gov considers equipment with an AFUE rating between 90 and 98.5 percent as high-efficiency, between 80 and 83 percent as mid-efficiency, and between 56 and 70 percent as low-efficiency. Simply put, the higher the AFUE rating, the more efficient the equipment.
Modern heating systems can achieve AFUE ratings of up to 98.5 percent, meaning they convert nearly all of the energy in their fuel to heat. To appreciate how far home heating technology has come, consider that a few decades ago, average ratings for furnaces and boilers ranged between 56 and 70 percent. If you were to upgrade from a furnace or boiler with an AFUE rating of 56 percent to one with an AFUE rating of 90 percent, you’d save two and a half tons of carbon dioxide emissions each year when you heat with oil.
Keep in mind that AFUE ratings aren’t the sole determiner of efficiency – the size of the equipment, ductwork, and airflow can all impact efficiency, among other variables. That’s why it’s important to speak to an expert if you’re considering an upgrade. Contact us today to arrange a consultation with one of our technicians and determine the right upgrade for your home.