You can find out your home’s heating and cooling efficiency by using the U.S. government’s Energy Star guidelines.
Energy Star is a federal set of standards providing unbiased information to HVAC owners and technicians. The performance of both furnaces and boilers is measured via annual fuel utilization efficiency (AFUE) guidelines. The Federal Trade Commission (FTC) demands that all new boilers and furnaces clearly display AFUE ratings so shoppers can make informed choices. AFUE measures how well the appliance turns energy to heat in a year’s span.
For example, a furnace with a 92 percent AFUE rating guarantees that 92 percent of the fuels’ energy is turned into heat. The remaining 8 percent leaves via a chimney or other source.
Heat lost in piping or ductwork doesn’t count for AFUE ratings because it’s impossible for an HVAC manufacturer to know the quality of your home’s pipes and ducts. That’s why it’s so important to have these parts regularly checked — pipe and duct heat loss can account for up to 35 percent of lost heat!
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In homes without chimneys, the electric furnace or boiler has an AFUE rating of 95-100 percent. Outdoor units will lose more heat (and be closer to the 95 percent mark). Still, 95 percent is efficient, and that’s good, considering electricity is a more expensive fuel. Installing a heat pump system can be a great way for all-electric heating sources to conserve resources.
Currently, the government doesn’t allow home installations of heating systems with an AFUE rating under 78 percent. Of course, this doesn’t consider old HVAC systems that are still humming along. Mobile homes have special considerations, and can legally have HVAC units with 75 percent AFUE. Soon, the AFUE minimum requirement will be dictated by type of fuel, weatherized versus non-weatherized units and type of home (mobile or not).
Boilers have different minimum AFUE rating demands, based on type of fuel and how the heat is created. For example, gas-fired, hot water boilers have a minimum 82 percent rating, while gas-fired steam boilers’ minimums are set at 80 percent.
A sign of an outdated (and likely now illegal!) boiler/heater is a continuous pilot light, a heavy heat exchanger and a natural draft from gases. You’re probably getting an AFUE of 56-70 percent with these museum pieces.
Fortunately, furnaces and boilers often can be retrofitted to provide more efficiency. Alternatively, it just might be time to upgrade your heating source. Contact Roberts Mechanical for a full heating and cooling inspection, and a professional opinion on whether your heating source is optimized.