Most U.S. homes are heated with either furnaces or boilers. Furnaces heat air and distribute the heated air through the house using ducts; boilers heat water, providing either hot water or steam for heating. Steam is distributed via pipes to steam radiators, and hot water can be distributed via baseboard radiators or radiant floor systems, or can heat air via a coil. Steam boilers operate at a higher temperature than hot water boilers, and are inherently less efficient, but high-efficiency versions of all types of furnaces and boilers are currently available.

Understanding the Efficiency Rating of Furnaces and Boilers

A central furnace or boiler's efficiency is measured by annual fuel utilization efficiency (AFUE). The Federal Trade Commission requires new furnaces or boilers to display their AFUE so consumers can compare heating efficiencies of various models. AFUE is a measure of how efficient the appliance is in the energy in its fuel over the course of a typical year.Specifically, AFUE is the ratio of heat output of the furnace or boiler compared to the total energy consumed by a furnace or boiler. An AFUE of 90% means that 90% of the energy in the fuel becomes heat for the home and the other 10% escapes up the chimney and elsewhere. AFUE doesn't include the heat losses of the duct system or piping, which can be as much as 35% of the energy for output of the furnace when ducts are located in the attic.

An all-electric furnace or boiler has no flue loss through a chimney. The AFUE rating for an all-electric furnace or boiler is between 95% and 100%. The lower values are for units installed outdoors because they have greater jacket heat loss. However, despite their high efficiency, the higher cost of electricity in most parts of the country makes all-electric furnaces or boilers an uneconomic choice. If you are interested in electric heating, consider installing a heat pump system.  The mid west is not the ideal location due to climate swings for this type of system.The minimum allowed AFUE rating for a non-condensing fossil-fueled, warm-air furnace is 78%; the minimum rating for a fossil-fueled boiler is 80%; and the minimum rating for a gas-fueled steam boiler is 75%. A condensing furnace or boiler condenses the water vapor produced in the combustion process and uses the heat from this condensation. The AFUE rating for a condensing unit can be much higher (by more than 10 percentage points) than a non-condensing furnace. Although condensing units cost more than non-condensing units, the condensing unit can save you money in fuel costs over the 15- to 20-year life of the unit, and is a particularly wise investment in cold climates.You can identify and compare a system's efficiency by not only its AFUE but also by its equipment features, listed below.

Old, low-efficiency heating systems: Natural draft that creates a flow of combustion gases

• Continuous pilot light
• Heavy heat exchanger
• 68% - 72% AFUE

Mid-efficiency heating systems:

• Exhaust fan controls the flow of combustion air and combustion gases more precisely
• Electronic ignition (no pilot light)
• Compact size and lighter weight to reduce cycling losses
• Small-diameter flue pipe
• 80% - 83% AFUE

High-efficiency heating systems:

• Condensing flue gases in a second heat exchanger for extra efficiency
• Sealed combustion
• 90% - 97% AFUE

• The following maintenance should be provided by a heating system professional.Check the condition of your vent connection pipe and chimney. Parts of the venting system may have deteriorated over time. Chimney problems can be expensive to repair, and may help justify installing new heating equipment that won't use the existing chimney.
• Check the physical integrity of the heat exchanger. Leaky boiler heat exchangers leak water and are easy to spot. Furnace heat exchangers mix combustion gases with house air when they leak, an important safety reason to have them inspected.
• Adjust the controls on the boiler or furnace to provide optimum water and air temperature settings for both efficiency and comfort.
• If you're considering replacing or retrofitting your existing heating system, have the technician perform a combustion-efficiency test

• CLEAN HEAT EXCHANGER & CAMERA INSPECT FOR CRACKS, CORROSION, RUST AND INTEGRITY FLAWS 
• CARBON MONOXIDE METER TEST
• CLEAN BURNERS & ADJUST FLAME OXYGEN LEVEL 
• CHECK FLUE PIPE FOR FURNACE AND WATER HEATER, MAKE SURE UNITS ARE EXHAUSTING PROPERLY 
• CHECK FLUE PIPE FOR FURNACE AND WATER HEATER, PITCH, SIZING, RUST AND CONFIGURATION 
• CHECK AND ADJUST GAS VALVE PRESSURES IF NECESSARY
• CLEAN BLOWER ASSEMBLY 
• OIL BLOWER MOTOR 
• CHECK BALANCE AND SPEED OF BLOWER MOTOR
• CHECK FAN CONTROL RELAY FOR PROPER DELAY CYCLE TIMING
• CHECK BELTS AND ADJUST TENSION IF NECESSARY
• CHECK AND CLEAN PILOT SYSTEM
• OHM HOT SURFACE IGNITORS, THIS CAN TELL THE STRENGTH AND LIFE OF PART
• CHECK ALL GAS PIPES AND SHUT OFFS FOR LEAKS AND PROPER CODE REQUIREMENTS
• CHECK ALL SAFETIES AND LIMITS SWITCHES
• CLEAN AND ADJUST ALL SAFETY CONTROL
• MICRO AMP FLAME RECTIFIER
• ADJUST TEMPERATURE RISE AND CALCULATE THE DIFFERENCE
• LUBRICATE ALL MOVING PARTS
• CHECK AND CALIBRATE THERMOSTAT
• CHECK COMPLETE FURNACE CYCLE
• CHECK AND CHANGE AIR FILTERS FOR FURNACE AND OTHER PIECES OF EQUIPMENT, WHEN NECESSARY; 
• PRICES VARY ON PRODUCT FOR AIR CLEANERS, HUMIDIFIERS DEPENDING ON MODEL 
• WE WILL LEAVE SERVICE INVOICE WITH CUSTOMER FOR REFERENCE & TECHNICIAN WILL ANSWER ALL
• ANSWER ANY QUESTIONS BEFORE LEAVING CUSTOMERS HOME
•       AND EVEN MORE
  

• CHECK OPERATING PRESSURES AND EFFICIENCY 
• CLEAN CONDENSING COILS
• LEVEL CONDENSING UNIT IF NECESSARY 
• CLEAN CONDENSING UNIT 
• CHECK REFRIGERANT LEVELS 
• CHECK TEMPERATURE ACROSS CONDENSING COIL  (CALLED SUPERHEAT)
• CHECK COMPRESSOR CONTACTOR, CONNECTIONS AND ERROSION 
• CHECK TEMPERATURE READING ACROSS EVAPORATOR COIL ABOVE FURNACE (TD) 
• CHECK TO MAKE SURE ALL COPPER LINES ARE PROPERLY INSULATED
• CHECK TO MAKE SURE THERE ARE NO PLENUM AIR LEAKS BY COIL PENETRATIONS
• CHECK VOLTAGE & AMPERAGE TO ALL MOTORS (CONDENSOR, FAN MOTOR & BLOWER MOTOR)
• LUBRICATE ALL MOVING PARTS
• CHECK LOW PRESSURE SWITCH CUT-OFF
• CHECK HIGH PRESSURE SWITCH CUT-OFF
• CHECK START CAPACITOR & POTENTIAL RELAYS
• CHECK BELTS & TENSION;TIGHTEN IF NECESSARY
• CHECK FOR VIBRATIONS & NOISE
• CHECK THERMOSTAT & WIRING; CALIBRATE IF NECESSARY
• CHECK FOR PROPER TEMPERATURE DROP
• CHECK THAT CONDENSATE DRAIN IS CLEARED AND DRAINING PROPERLY
• CHECK COMPLETE AIR CONDITIONING CYCLE 
• CHECK & CHANGE FILTERS FOR ALL PIECES OF EQUIPMENT, WHEN NECESSARY; PRICES WILL VARY ON
• FILTERS FOR FURNACES, AIR CLEANERS & HUMIDIFIERS DEPENDING ON MODEL
• WE WILL LEAVE SERVICE INVOICE WITH CUSTOMER FOR REFERENCE & TECHNICIAN WILL ANSWER ALL
• ANSWER ANY QUESTIONS BEFORE LEAVING CUSTOMERS HOME