|Comparing energy efficiency of different
brands of heating and cooling equipment is relatively easy. Although the
rating systems are standardized, allowing you to make a fair comparison,
there are three different rating systems used. Each rating is used for a
specific type of product(in other words, all furnaces use the same system,
heat pumps use a different system, an so on). They are:
The efficiency of a furnace is measured in a rating known as AFUE
(Annual Fuel Utilization Efficiency). A lot like your car's miles per
gallon rating, AFUE tells you how efficiently the furnace converts fuel
(gas or oil) into heat. An AFUE of 80% means that 80% of the fuel is
used to heat your home, while the other 20% basically goes up the
The government mandated a minimum AFUE rating for furnaces installed
in new homes is 78%. (In contrast, many furnaces manufactured before
1992 had AFUE ratings as low as 60%, so nearly half the fuel was
being wasted.) Furnaces with AFUE ratings of 78% to 80% are considered
"mid-efficiency"; those with ratings of 90% or higher are
known as "high efficiency." The maximum furnace efficiency
available is around 96.6%.
In general, a higher efficiency furnace usually means two things:
If you have an older furnace (with an AFUE of about 60%), you could save
up to 60% on your heating bills by replacing it with a new
high-efficiency furnace. So the cost to replace your old, inefficient
furnace is paid back through lower utility bills.
- higher price
- lower monthly operating cost
If you live in a cold climate, you could see a
payback in a few short years. If you live in a moderate climate, it
might make more sense to purchase a mid-efficiency furnace. Your dealer
can use heating data from your area to help you determine about how long
it would take you to recover the additional cost of a high-efficiency
model in energy savings. (Of course, after the payback, you continue to
save on your energy bills for the life of the system.)
Cooling efficiency for air conditioners and heat pumps is indicated
by a SEER (Seasonal Energy Efficiency Ratio) rating, which tells you how
efficiently a unit uses electricity. The higher the number, the greater
The typical SEER rating of units manufactured prior to 1992 is about
6.0.Now, the government mandated minimum is 10.0 SEER. High-efficiency
units have a SEER of at least 12.0; the maximum available is about 17.
Heat pumps also have heating efficiency ratings, indicated as an HSPF
(Heating Seasonal Performance Factor). In general, the higher the HSPF
rating, the less electricity the unit will use to heat your home.
The government mandated minimum heating efficiency standards for new
heat pumps is 6.8 HSPF. Most heat pumps manufactured before 1992 have
HSPF ratings below 5.0. Today, an HSPF of 7.5 or higher is considered
"high-efficiency"; the maximum available is 10.0.
Higher efficiency in heat pumps and air conditioners
usually means higher cost but lower utility bills. If you live in a warm
and/or humid climate, you will probably see the higher cost of a
high-efficiency air conditioner or heat pump paid back (through lower
utility bills) in a few short years. Ask your dealer to help you
determine about how long it would take you to recover the additional
cost in energy savings. Of course, after the payback, you continue to
save on your energy bills.
Matching Your System for Optimum Efficiency.
other factor that affects the efficiency of your air conditioning or
heat pump system: the indoor coil. (Your heat pump or air conditioner is
a "split system," which means that there is an outdoor unit,
or condenser, and an indoor unit, or evaporator coil.) If your
condensing unit is not matched with the proper indoor coil, it may not
give you the stated SEER and/or HSPF ratings and could even develop
performance problems. (It's kind of like putting two new tires on one
side of your car and leaving the old, worn-out ones on the other side.
You'd probably be disappointed with both the performance and the miles
per gallon you get.) When you're replacing an existing system, make
sure you replace both units so your new condensing unit will give you
optimal performance, efficiency and comfort.