What you Need to Know about the New Minimum Efficiencies Heating Standards

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April 2, 2015

January 1, 2015, marked the beginning of a new era of sorts, both for the HVAC system manufacturing industry, as well as for furnace and boiler companies. This change, brought about by updates to the minimum efficiencies heating standards, will obviously also reflect on the average consumer. In today’s post, we provide a brief overview of these new minimum efficiencies and explain what they mean in reference to various types of heating equipment. We also explain how these changes will affect you, the household consumer.

New Minimum Efficiencies Heating StandardsHow heating efficiency ratings for furnaces and boilers work

The difference between furnaces and boilers is that the former use heated air, relayed through ducts, to heat a home, while boilers heat water, and distribute either steam through pipes or hot water through radiators in the baseboard or heat radiant floors. Alternatively, some boilers also heat air through coil elements. By and large, there are high-efficiency models of all the above mentioned heating systems, though steam boilers require higher temperatures to turn water into steam and are generally less efficient.

The AFUE rating for furnaces and boilers

The main index, which helps compare the way in which various furnace and boiler models observe minimum efficiencies heating standards, is the AFUE. AFUE stands for annual fuel utilization efficiency and displaying this index on all versions of furnaces and boilers is mandated by the Federal Trade Commission. In a nutshell, this index, which represents the ratio of heat output per fuel energy consumed, will tell you how efficiently a given system can convert said energy into fuel over the course of a standard year. Bear in mind that this index cannot keep track of duct or pipe losses and such deficits can amount to as much as 35 per cent. This is especially the case when said piping or duct systems are located in improperly conditioned rooms, such as the attic or the garage.

The more losses a furnace or boiler experiences, the less fuel efficient it will be. Electric furnaces and boilers, for instance, require no chimneys, which means their AFUE rating is between 95 per cent (for outdoor units, which lose some heat through their jackets) and 100 per cent. Though they may be efficient, they’re not exactly affordable. Electricity is an expensive commodity even in developed countries, and the U.S. is no exception in this respect. The U.S. Department of Energy recommends that household owners consider heat pumps instead of electric boilers or furnaces.

Current minimum efficiencies heating system manufacturers must observe

At the moment, furnaces which produce warm air, run on fossil fuels, and are non-condensing have a minimum heating efficiencies rating of 78 per cent. The exception to this rule is the case of units especially designed for use in mobile homes, whose minimum AFUE index is 75 per cent. In broad strokes, the current minimal requirements for AFUE indexes take into account the type of fuel the furnaces use, as well as whether or not the unit is weatherized. Non-weatherized furnaces are those designed to only be used indoors. The minimum efficiencies heating furnace manufacturers need to observe are listed in the chart below. They have been in effect since May 1, 2013 for non-weatherized units, and since January 1, 2015 for weatherized ones.

Product type

Minimum AFUE rating

Non-weatherized gas-fueled furnaces (including those designed specifically for mobile homes)


Non-weatherized oil-fueled furnaces (except for those designed for mobile homes)


Oil-fueled furnaces designed for mobile homes


Weatherized gas-fueled furnaces


Weatherized oil-fueled furnaces


Electric-fired furnaces


Minimum AFUE index requirements are approached from a slightly different perspective for boilers. They are grouped by the type of fuel they use, as well as by the medium they heat (i.e. water or steam). Bear in mind that steam boilers that run on oil cannot have constantly burning pilots, while hot water boilers always need to be equipped with a way to adjust the temperature of the water to match the heating load.

Product type

Minimum AFUE rating

Gas-fueled hot water boiler


Gas-fueled steam boiler


Oil-fueled hot water boiler


Oil-fueled steam boiler


It’s also important to bear in mind that condensing heating units, i.e. those which can produce condensation from the heated water vapor and subsequently use this for heating, can have comparatively higher AFUE ratings than non-condensing units. The difference can run as high as 10 per cent. Condensing furnaces and boilers can be more expensive than non-condensing units, but they’re usually more fuel efficient and can have a lifespan that’s longer by some 15 to 30 years. When deciding what type of heating system to have installed in your home, it’s also a good idea to take a good look at the unit’s components. Old, low efficiency models run on a natural draft that helps the fuel flow and have a continuously burning pilot light. Meanwhile, models of average efficiency have the flow of air and fuel controlled with an exhaust fan, no pilot lights, smaller flue piping requirements, and are usually smaller and more compact. Finally, modern, high-efficiency furnaces and boilers come with a second heat exchanging unit, which helps condense flue gas and run on sealed combustion.

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