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Older heating systems can burn money

Gary Dymski | Home Work

December 12, 2007

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Can you tell me a little about the term Annual Fuel Utilization Efficiency (AFUE), which is applied in the ratings of furnaces and boilers? On an older unit, where can I find the AFUE? Also, can you tell me about paybacks on installing a new furnace or boiler? -- John Barry, Oyster Bay

The Annual Fuel Utilization Efficiency is a rating that describes in percentage how efficiently a furnace or boiler converts fuel to energy. A higher AFUE rating means a more efficient unit. AFUE ratings are printed in the owners' manuals of every furnace or boiler. If you don't have the manual, the information -- along with model number, size and serial number -- often is located on a plate or label inside the access door or panel of the unit.

I'm often asked about paybacks on new furnaces and boilers. (Furnaces heat air and distribute it through ducts; boilers heat water, providing either hot water or steam for heating.) Is it really worth it to replace an older heating system? Well, that depends on the age and size of your current unit. Generally, if your current unit is 15 to 20 years old, chances are you will end up saving money over the long haul. The other factors are increases in fuel costs and the planned length of stay in your home.

There is an equation, which I'll share with you in a moment. But let's get back to AFUE.

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Heating units built during the 1960s or earlier have low AFUEs. Gas-fired furnaces and boilers can have AFUEs as low as 60 percent; oil-fired units can be around 65 percent. If you think in terms of dollars, I translate this to mean that for every dollar of fuel being burned, only 60 to 65 cents is used for heat. The remaining 30 to 35 cents goes up the chimney or is vented from the house as exhaust. Only in the late 1980s and early 1990s did the minimum AFUE on gas- and oil-fired systems change considerably. Today, minimum AFUEs are 78 for fossil-fueled warm-air furnaces and 80 for fossil-fueled boilers.

By 2015, the Department of Energy is expected to increase minimums. Gas furnaces will be at 80 AFUE; gas boilers, 82; oil furnaces, 82; and oil boilers, 83.

Some experts -- especially oil-heat advocates -- say AFUE does not consider factors like idle loss in hot-water heating systems. Idle loss deals with two areas of heat loss in residential systems called standby loss and jacket loss. In short, some older oil systems can actually be made more efficient with heat-retention burners. Replacing an oil-hot water system that is 22 years or older often is a good option. On newer systems that are running efficiently and have been serviced annually by a licensed technician, installing a new heat-retention burner (about $600) can save money.

To determine how much homeowners can save if they upgrade to a new heating system, we'll get help from the American Council for an Energy-Efficient Economy. The Washington, D.C.-based nonprofit uses two ways to calculate savings. One is annual savings per $100 of fuel purchased. Calculations are based on a chart at aceee.org and the annual fuel bill of a household. So when replacing a gas furnace, if the old AFUE is 65 and the new is 90, annual savings could reach $350 or more, the ACEEE says.

Another calculation identifies return of investment in a percentage. This is determined by the equation: ROI = first-year savings ÷ installed cost. So, with a savings of $350 and an installation cost of $2,500, the return is 14 percent. At that rate, a homeowner's payback time would be a little more than seven years.

The Energy Star program lists boilers and furnaces, by model number, model name and AFUE rating, at Energystar .gov.

What's it all mean? If you have an oil-fired system older than 20 years or a gas-fired system older than 15 years, you might realize significant savings with a replacement. If I were buying new, I'd make sure my new unit had the highest efficiency rating possible. The cost of fuel will only increase over time.

In your Sunday article, "Thwarting hidden dangers at home," you made a mistake about Radon. Radon is a radioactive gas produced from the decay of uranium in granitic rocks. Thus radon is not a hazard in most areas, only those where the bedrock contains uranium. I have often complained to managers in home improvement stores on Long Island that selling radon test kits is a waste of money and preying on people's fears. -- Christopher Visco, Patchogue

While instances of radon are more common in areas with granitic soil, as you state, you might be surprised what recent testing revealed about Long Island. In August of this year, the New York State Department of Health tested for radon levels in counties and towns across the state. On Long Island, both counties were included in random testing of residential basements. In Nassau County, out of more than 650 homes tested, about 36 showed radon levels of between 4 and 20 pCi/L (picocuries per liter of air). Levels between 4 and 20 pCi/L generally require some type of action, including calling in a trained professional.

In Suffolk County, 398 homes were tested, and 25 showed levels between 4 and 20 pCi/L. One Smithtown home was found to have a pCi/L reading of more than 20, which is a health risk.

You can see test results at http://www.health.state.ny.us/environmental/radiological/ radon/maps_statistics.htm.

Actually, radon is the byproduct of radium, which is a byproduct of decaying uranium. Because it is the second-leading cause of lung cancer, after smoking, radon is a threat. The EPA says, "All homes should test for radon, regardless of geographic location or zone designation."

New Yorkers can order a test kit for $6.75 at health.state.ny.us/environmental/radiological/radon/testkit.htm. Kits also can be ordered by writing the N.Y. State Department of Health, Bureau of Environmental Radiation Protection, 547 River St., Flanigan Square, Room 530, Troy, NY 12180-2216 or calling 800-458-1158, ext. 27556, or 518- 402-7556.