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:
- AFUE (gas heating)
- SEER (cooling)
- HSPF (heat pump heating)
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 chimney.
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:
- higher price
- lower monthly operating cost
If you have an older furnace (with an AFUE of about
60%), you could save up to 40% 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.
Payback
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 efficiency.
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.
Payback
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
There’s one 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.
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