UNDERSTANDING BOILER & FURNACE EFFICIENCY RATINGS
Let’s start with the bad news. The cost of heating your home is on the rise. The good news? Technological advances have given homeowners more energy efficient options to heat their homes.
The most common heating systems in the Pittsburgh region are furnaces and boilers. The energy efficiency of both is measured by an Annual Fuel Utilization Efficiency (AFUE) rating. This is a measurement of the appliance’s efficiency in using electricity or fossil fuels (gas or oil) for heating over the course of a year.
HOW IS THE AFUE MEASURED?
The AFUE basically compares the amount of heat produced to the amount of energy needed to produce that heat. For instance, a unit with an 85 percent AFUE loses 15 percent of its energy in the heat-producing process. 85 percent of the fuel heats your home.
When you’re shopping for a new furnace or boiler, the unit’s AFUE rating should impact your decision-making. Generally, the higher AFUE you see, the more you’ll save on heating costs in the long run. You’re getting a greater amount of heat while using less energy.
Just keep in mind the unit itself and perhaps its installation will most likely be pricier. Also know that this rating doesn’t factor in potential heat loss through ducts. As much as 35 percent of a home’s heating efficiency can be lost through attic ductwork or leaky ducts throughout the house. There’s just no way to factor this into a rating since ductwork heat loss will vary from home to home.
Energy efficient heating systems are typically broken down into three categories.
Also referred to as a “base model”, these furnaces and boilers usually have an AFUE rating of 78 to 80 percent. Comparatively, most older furnaces in homes have about a 60 to 70 percent efficiency rating and older boilers range from 55 to 65 percent. This means switching from an older system to a newer affordable base model can save significant money over time.
These units have slightly higher efficiency ratings. Mid-efficiency furnaces (gas and propane) and boilers have AFUEs up to 83 percent. A furnace fueled by oil can go up to 87 percent.
Gas and propane condensing furnace units have AFUE ratings from 90 to 96 percent. Their higher efficiency is due to a second heat exchanger that extracts heat from exhaust gasses otherwise vented outdoors by a lower efficiency unit. This means these furnaces can do more with less fuel.
These units also kick on with an electronic ignition rather than a gas powered pilot light burning at all times. This of course further reduces energy consumption. High-efficiency condensing boilers have an AFUE up to 98 percent.
Although these high-efficiency condensing boilers and furnaces tend to cost more than their non-condensing counterparts, they can save homeowners significant money over a unit’s 15 to 20-year life.
ALL-ELECTRIC FURNACES OR BOILERS HAVE HIGHEST AFUE
AFUE ratings for an all-electric furnace or boilers don’t have to account for flue loss and can be as high as 95 and 100 percent. While these units may have higher efficiency ratings, the cost of electricity to run them is usually higher. This means they’re ultimately not the most cost-effective option.
HOW TO IDENTIFY OLDER UNITS WITHOUT AN AFUE RATING
Unfortunately, older heating systems usually don’t have an AFUE rating or it’s been removed by the time you’ve bought the home. Older low-efficiency furnaces can be spotted by the need for a continuous pilot light. The style of furnace where you have to relight the pilot light if the flame goes out. This type of older furnace can be just 56 to 70 percent efficient. That’s literally money blowing away.