home cooling.q - North Little Rock Electric Department

home cooling.q - North Little Rock Electric Department
HOME COOLING
HOME SERIES
INSIDE
LOW-TECH ALTERNATIVES . . . . 3
MAKING THE MOST OF YOUR A/C . . 10
BUYING A NEW COOLING UNIT . . .12
Low-Tech Ways to Cool Off
• Keep your interior lights low
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or, if possible, completely off
during the daylight hours.
Wait until the cooler evening
hours to use your oven. Or
better yet, use a microwave
or toaster oven to cook foods
whenever possible.
Use kitchen and bathroom
exhaust fans to vent heat
and humidity outside.
Caution: Don’t use exhaust
fans any longer then necessary or they can blow out all
the cooled air in your home.
Close your drapes or window
blinds during the daylight
hours.
Keeping your cool
Americans spend approximately $11.9 billion on air conditioning
(A/C) each summer. Individual homeowners often spend a significant
portion of their summer energy budget on air conditioning.
Fortunately, there are ways to cut the cost of running your A/C
unit and still keep your cool. The information in this booklet will
cover “low-tech” alternatives to air conditioning, help you use your air
conditioner more efficiently and give you tips on upgrading or replacing your existing A/C unit.
We hope you’ll find this booklet informative and useful and that
you’ll look for other Arkansas Energy Unit Home Series booklets to
help maximize your home’s energy efficiency.
Four Basic Steps
Keeping your home cool and comfortable at an affordable cost
can be accomplished in four basic steps:
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Reducing the cooling load on your house
Exploring alternative cooling methods
Increasing the efficiency of your existing air conditioner
Buying a new, energy-efficient air conditioner
Cutting the Cooling Load
The best strategy for keeping your house cool in the summer is to
prevent it from getting hot in the first place. This means trying to keep
the outside heat and the direct sunlight from getting inside; reducing
the amount of heat given off by inefficient appliances, lights and
unwrapped water heaters and reducing the amount of time you use
other heat-generating appliances like your stove.
During Arkansas’ hot, humid summers, the greatest energy use goes
to cool your home. The major sources contributing to higher cooling
energy use are the sunshine that turns to heat after it passes through
the windows, the outside heat and humidity that enter through small
and large leakage areas, internal heat from lights and appliances, and
conduction of heat through the walls and ceiling.
It makes sense to reduce these cooling loads before investing in a
new air conditioner. Also, if you can reduce the heat entering your
home, you will be able to get by with a smaller, less expensive A/C
unit.
“LOW-TECH” ALTERNATIVES
The Hot Spots
Sunlight, or solar energy, hits the roof and comes through the windows, accounting for most of the heat gain inside a house. Therefore,
the most important places to use shading are the roof and windows.
Energy conservation measures that block the sun before it strikes
the roof or windows are the most effective. Trees and other plants that
provide shade are your best long-term investment for reducing cooling
costs.
Roofs
Solar heat gain is greatest in homes with dark roofs, inadequate insulation and poor roof ventilation. Heat gain can be reduced by onethird by shading your house with trees, adding insulation and ventilating attics.
Air Leaks
Air leaks in your home can be costly problems if you have air conditioning, especially in humid climates like Arkansas. Measuring air
leaks with a blower door test (Page 6) is an effective way to identify
where air leaks are in your home.
Ducts
If you have central air conditioning, one of the fastest ways to save
energy and money is to seal all leaks in the ductwork. Savings on A/C
costs of 10% to 25% are typical and 30% to 50% are possible. More
information on ducts can be found on page 11.
Trees
Trees and landscaping are the most effective measures for blocking
solar heat. Well-planned landscaping can reduce an unshaded home’s
summer A/C costs by 15% to 50% depending on the R-value of the
attic insulation.
In fact, the temperatures directly under trees can be up to 25°F
cooler than air temperatures around nearby blacktop. Trees also are a
good investment. Studies by real estate agents and professional
foresters estimate that trees raise a home’s resale value 7% to 20%.
Summer
Winter
Figure 1: Deciduous trees
provide shade in the summer and
warming sun in the winter.
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Additionally, the more shade you have, the more effectively you
can reduce the size of your air conditioner as well as your cooling
costs. Shade makes the air around the house cooler and it prevents
solar heat from building up indoors.
Deciduous trees — which are leafy during the warm months and
bare in winter — can screen out the summer sun, yet allow winter sunshine to come through their branches and warm your home (Figure 1).
Trees should be planted on the southeast and west sides of your house
for the maximum shading effect. Not only will they help lower your
energy costs over the years, but they’ll make your home a greener and
more beautiful place to live.
Windows
Single-pane, unshaded windows let in about 85% of the heat in the
sunlight. The following options can block 60% to 90% of the solar heat
that currently enters your windows.
Sun Screens: These are often the least expensive option for maintaining a view and blocking the sun. The fabric absorbs 65% to 70% of
the solar heat before it enters the house. The screen must be installed
on the exterior of a window to be effective.
Reflective Films: Metalized plastic window films can
block 50% to 75% of the solar heat. Because reflective window films block sunlight in addition to solar heat, consumer
acceptance has been slow. Newer films on the market transmit more light. Installation is moderately difficult.
Interior Window Treatments: Window treatments that
have reflective, metallic or bright-white surfaces, can effectively block solar heat. For example, an opaque roller shade
with a white surface facing outward stops roughly 80% of
the solar heat. White venetian blinds and white slim shades
stop about 40% to 60% of the heat.
Figure 2: Common heat sources in
a house include windows, lights,
stoves and appliances.
“Cool” Hot Weather Habits
Making some minor changes in your personal habits during the
dog days of summer is another way to reduce your need for air conditioning and add to your energy savings. While the following lifestyle
habits may not always be possible, incorporating some or all of them into
your summer routine will definitely help you stay cool and save money
on your home cooling costs.
• Keep your interior lights low or, if possible, completely off during
the daylight hours. Light fixtures generate heat, and therefore add
to your cooling costs (Figure 3). Appliances such as TVs and stereos
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also generate heat, so it helps to turn them off when no one is using
them.
Wait to use your oven and other heat-generating appliances until the
cooler evening hours. A hot oven will quickly heat up your kitchen
and the adjoining rooms.
Microwavable foods, as well as uncooked sandwiches, salads and
fruits are good options for keeping your home cooler on hot days.
If you use your clothes dryer, make sure it vents to the outside; otherwise, the heat and humidity will build up in your house.
If you are going to use your A/C, use energy-efficient thermostat
settings between 74°F and 78°F.
If it is humid and if you use your A/C regularly, you are better off
not opening your windows on cooler days or at night. This is
because your A/C unit will have to work extra hard to remove the
humidity from your house before it can begin to cool your house.
Figure 3: Compact fluorescent
lights add less heat to the house
than incandescent lights.
HOME TIGHTENING
Caulking, weatherstripping and insulation are some of the best
tools for preventing unwanted heat and moisture from entering your
home in the summer. They are also important in reducing heat loss in
the winter months.
There are many places where air can leak into and out of your
home. A good rule of thumb is to seal the attic and basement air leaks
first with caulk and weatherstripping. The following checklist will help
you locate common trouble spots for air leaks.
Figure 4: Holes around recessed
lights, wiring, pipes and other openings in insulated ceilings can result in
a tremendous amount of heat loss.
band
joist
sill plate
Air Leak Trouble Spots
THE ATTIC:
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Holes in the attic floor and walls
Doors and hatches to the attic
Plumbing stacks
Attic knee walls/storage drawers
foundation
Figure 5: Get rid of drafts along the
floor by caulking along the sill plate
and band joist in the basement.
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THE BASEMENT:
• Around the sill plate and band joists
• Around basement windows
• Ducts
• Openings in the basement walls and ceiling including dryer vents,
electrical wiring, plumbing stacks, etc.
THE MAIN LEVEL:
• Around the chimney and fireplace dampers
• Around windows, doors, trim and baseboards
• Electrical outlets and other exterior wall openings
THE OUTSIDE:
• Cracks in exterior siding
• Around windows and doors
• Around outdoor faucets, vents and electrical outlets
sheet metal
Figure 6: Heat can escape around
the chimney if it isn’t properly
sealed.
A more precise way to find air leaks is to have a blower door test
done on your home. A blower door is a device that depressurizes a house,
making it possible to measure the amount of air leakage and pinpointing
air leaks that cannot otherwise be seen. This test allows you to actually
feel where air loss is occurring.
Blower door tests can also identify health hazards created by
backdrafting. These tests are also able to project whether your home
has enough natural infiltration — the ability to draw in fresh air — to
have good indoor air quality. Consult your yellow pages or call the
Arkansas Energy Unit at 501-682-7319 or visit our Web site at
www.1800ARKANSAS.com/energy/ for a list of certified energy raters.
After you have sealed air leaks in your home, make sure your home
is properly insulated. Insulation helps keep homes cool in the summer,
and warm in the winter. For more detailed information on caulking,
weatherstripping and insulation, consult the Home Series issues, Home
Tightening and Insulation.
ATTIC VENTILATION
Your roof can absorb a tremendous amount of heat in the summer,
and if the attic isn’t properly insulated and ventilated, its temperature can
reach as high as 150° F. This is like having a gigantic radiator above your
living spaces.
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Attic ventilation serves two purposes. First, it cools hot attics during
the summer months. Second, it removes moisture from insulation and
other building materials that may accumulate in the attic during the
winter months.
In the summer, the sun’s heat puts a strain on your home’s airconditioning system. This heat builds up in the attic and can be stored
there even on cool summer nights. This means higher air-conditioning
bills and increased strain on all the components of the air-conditioning
system. By ventilating your attic, you can dramatically reduce both of
these problems.
Ventilation is needed in two areas to ensure proper air flow through
the attic. First, vents are needed at or near the top of the roof using roof,
gable, turbine or continuous vents. Second, soffit vents should be at the
lower edge of the roof to allow air to circulate naturally. A combination
of high and low vents and a combination of continuous soffit vents and
continuous ridge vents is the most effective option.
Attics without a ceiling vapor barrier should have a minimum of
one square foot of vent area for every 150 square feet of ceiling area.
two types of gable vents
soffit vent
turbine vent
roof vent
continuous ridge vent
Figure 7: Five common attic vent types.
FANS
Fans do not cool the room they are in. They do, however, create a
cooling effect by moving air across the skin. To receive the costsaving benefit of a floor, table or ceiling fan, turn the thermostat up a
few degrees.
• Ceiling Fans: These fans are common in southern climates. They
are probably the best way to circulate air in rooms, and they’re a
great way to supplement your air conditioning. Unlike window fans
and smaller oscillating fans, ceiling fans are permanent fixtures that
operate from a wall switch or pull string. There should be at least
seven feet between the fan and the floor for safety, but fans that are
too close to the ceiling, such as “ceiling hugging” models, may not
provide adequate air flow.
Generally speaking, the larger the fan’s blades are, the greater
the air movement and the quieter the fan will be (see Table A). A
good ceiling fan should create enough air movement that you will
be comfortable at 82°F and 80% relative humidity. If you’re using
the fan to supplement or circulate air conditioning, you should be
able to raise the thermostat of the A/C unit a full 4°F above the
standard 78°F setting and still be comfortable. This is significant
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because for every degree you raise your air conditioner’s thermostat above 78°F, you save about 3% to 5% on your cooling costs.
You should not use both your air conditioner and a ceiling fan
unless you first raise the temperature setting on the A/C unit;
otherwise, you’ll be wasting energy and needlessly increasing
your electric bills. For the same reason, you shouldn’t leave ceiling fans running in unoccupied rooms.
TABLE A: SIZING YOUR CEILING FAN
Room Area (sq. feet)
100
150
225
375
400+
Minimum Fan Diameter
36 inches
42 inches
48 inches
52 inches
2 fans needed
Sources: Consumer Guide to Home Energy Saving (1995) by the American Council
for an Energy Efficient Economy.
Figure 8: Floor fans, table fans and ceiling
fans are the most cost-effective electric
cooling devices available. They should be
used to create a wind-chill effect while
reducing the need for whole-house fans,
evaporative coolers or air conditioners.
Figure 9: If possible, locate room
air conditioners on a north wall or a
wall that is shaded.
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• Oscillating Fans: These fans have heads that pivot. If you just
want to circulate air in a small room, or extend the cooling range
of a window-mounted air conditioner, an oscillating fan will probably be sufficient for your needs.
• Exhaust Fans: Kitchen exhaust fans mounted above ranges
help remove the heat and humidity created during cooking.
Bathroom exhaust fans help remove the heat and humidity caused
from baths and showers. Make sure that the vent fans are periodically cleaned and that they vent properly to the outside to effectively remove excess heat, moisture and odors. Also, don’t leave
your exhaust fan on longer, or at a higher speed, than necessary. In
just one hour, these fans can blow a house full of cooled air outside. Food odors and oven heat usually can be removed within 15
minutes or less.
There are two important items to consider when selecting a
ventilation fan:
1. How many cubic feet per minute (cfm) can the fan push? A
100 cfm fan is typically enough for a kitchen and a 50 cfm
fan is usually adequate for the washroom/bathroom.
2. How noisy (rated in “sones”) is the fan? For quiet operation,
look for fans with a sone rating not greater than 1.5.
Since new homes are being built tighter than in the past, it is
important that fans not be oversized. Stoves with built-in fans
are inefficient at removing moisture and they remove a tremendous amount of air. This excess air removal pulls in outside air
and also might create back drafting of vented gas appliances.
GOOD OPERATING HABITS FOR YOUR A/C
A spring inspection and tune-up of your A/C unit is an important
step to improve its efficiency and increase its lifespan. Tune-ups
should always be done by a qualified service person. Make sure that
you call someone qualified to work on your particular A/C model. The
following items should be checked:
• Check thermostat settings to ensure the cooling system turns on and
off at the right temperature.
• Clean evaporator and condenser air-conditioning coils. Dirty coils
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reduce the system’s ability to cool a home and cause the system to
run longer, costing you more energy dollars and decreasing the life
of the equipment.
Check refrigerant pressures and adjust charge if necessary. Too
much or too little refrigerant charge can damage the compressor in
your air conditioner, reducing the life of your equipment and
increasing costs.
Clean and adjust blower components to provide greater comfort levels.
Measure airflow over the coils. Adequate airflow will improve
equipment efficiency and reliability. With inadequate airflow, your
system can lose up to 15% of its efficiency.
Tighten all electrical connections and measure voltage and current
on motors. Faulty electrical connections can cause unsafe operation of your system and reduce the life of major components.
Lubricate all moving parts. Parts that lack lubrication cause friction
in motors and increase electrical energy consumption.
Check and inspect the condensate drain. If plugged, it can cause
water damage in the house, affect indoor humidity levels, and breed
bacteria.
Figure 10: Clean AC air filters
regularly.
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• Check controls of the system to ensure proper and safe operation.
• Check the starting cycle of the equipment to assure the system
starts, operates and shuts off properly.
There are also some types of routine cleaning that you can do to
keep your A/C unit running smoothly. They include the following:
• Clean or replace filters monthly.
• Clean the blower’s fan blades.
• Carefully clean the outside condenser coils as often as necessary
(when dirt is visible).
• Remove debris from around the outside compressor.
Figure 11: The outside compressor
for a central air conditioner should
be shaded from direct sun.
MAKE THE MOST OF YOUR A/C
In addition to the annual checkup and routine cleaning, there are
many things that you can do throughout the summer to ensure that
your A/C unit works efficiently.
• Efficient thermostat settings are one of the easiest and most
effective ways to save money on cooling costs. For each degree
Fahrenheit you raise your thermostat, you can reduce your A/C
unit’s energy use by 3% to 5%. For example, if you raise your thermostat from 74° F to 78° F (the setting recommended by the
Department of Energy), you’ll automatically save 12% to 20% on
cooling costs. You should never set the thermostat any lower than
72° F. If you must leave your A/C unit on overnight, set the thermostat slightly higher than usual (ideally 78° F to 80° F).
vapor
barrier
metal
tape
Figure 12: Seal joints on ducts with
mastic or an approved tape. Then
wrap insulation around the duct.
• Choose a good location for the outside portion of your central
A/C unit or window unit. Avoid unshaded areas on the south or west
sides of your home. It’s best to put this unit on the north or east side
of your home, where it will be shielded from intense sunlight.
Doing this will automatically increase its efficiency by 10%.
If it isn’t possible to place your A/C unit in one of these locations, shrubs or trees can be planted by the unit to provide natural
shade. Be careful, however, not to plant shrubs too close. Leave
four to five feet of open air between any shrubs or trees and the unit
to ensure proper ventilation.
• Keep the grass around central A/C trimmed so that air can
circulate properly. When mowing around the unit, be careful not to
blow debris or grass clippings into it.
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• Avoid locating the indoor thermostat near windows or
heat-generating appliances like ovens and refrigerators. Also,
keep lamps and televisions away from your thermostat. The heat
from these can “trick” your A/C unit into thinking that your house
is warmer than it actually is, thus forcing the unit to run more often
than necessary. The ideal location for the thermostat is in the room
where you spend the most time.
• Clean and/or replace the filters on your A/C unit. This can
dramatically increase your savings and reduce the load on your A/C.
Dirty filters cause your A/C unit to work harder when circulating air
and leads to both higher energy bills and a shortened life span. Some
types of filters can be rinsed out and reused.
• Check your air ducts for leaks and obstructions. A recent
study of residential central A/C systems found that almost 100% of
homes had leaky ductwork, which means that there’s a good chance
that your A/C system is losing some of its cooled air. Duct system
leaks can account for up to 25% of the energy your central heating
and cooling system uses if your ducts run through an unheated basement, attic or under a trailer home.
Most air leaks in central A/C units occur in the return air plenum.
Plenums are the large ducts above or below the air handler. When
these leaks occur, warm air is pulled into the system and the cooled
air is heated up. If your central A/C system is unable to cool your
home satisfactorily, leaky ducts may be the cause. Ducts can be
sealed and insulated and thus improve your A/C systems efficiency
(Figures 12 and 13).
• Use the correct refrigerant charge. This can greatly affect
your air conditioner’s efficiency. A system that is undercharged by
10% may have a drop in efficiency of 20%. By the same token, the
refrigerant should never be overcharged because it can cause the
refrigerant and oil to flood and damage the A/C unit.
Only a professional service person should check and recharge your
air conditioner’s refrigerant. Refrigerants never “wear out” and refrigerant coils are completely sealed, closed systems. Therefore, if your
refrigerant coils were properly charged during installation, but later
need to be recharged, you have a leak in the system. Failure to repair
the leak has two consequences: First, it allows refrigerants to leak into
the atmosphere and damage the ozone layer. Second, moisture can
enter the A/C system and combine with the chlorine and fluorine in
the refrigerant to form acids which, over time, will damage the A/C’s
compressor and coils.
Figure 13: Create a continuous
vapor barrier on the ducts by sealing the insulation seams with metal
tape.
Most Common Problems for
Central A/C Systems
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A/C equipment sized incorrectly
Ductwork leaky or improperly sized
Dirty condenser coils
Improper refrigerant charge
Location is in direct sun
Trees and shrubs too close to unit
Dirty filters
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• Clean the indoor and outdoor coils of your central A/C
system. These coils are the heat exchangers between the refrigerant and the surrounding air. The indoor coil is cold, and as air moisture condenses on it, it filters out impurities which can build up very
quickly and hamper the coil’s performance. A recent study found
that indoor coils lose about 8% of their efficiency each year due to
dirt buildup. Indoor coils are sometimes difficult to find and access
and extremely fragile. However they can be cleaned with a soft
cloth and warm, soapy water. Outdoor (condenser) coils are easier
to reach and can be cleaned the same way. Both types of coils need
to be treated gently. If you have any questions on your A/C unit’s
care, consult the manufacturer’s recommendations.
BUYING A NEW COOLING UNIT
outside unit
inside unit
compressor
coils
Figure 14: Room air conditioner.
If your existing A/C unit is more than 15 years old, it’s probably
inefficient and you should consider replacing it with a newer unit. This
is also true if your current system has compressor problems, or if the
cost of repairs approaches the cost of a newer unit.
When buying a new home-cooling system, there are three primary
considerations to keep in mind: efficiency, type and size. In Arkansas,
there are two prevalent types of air conditioners used: room air conditioners and central air conditioners.
Heat pumps and ground-source systems are other options to consider.
These units provide high-efficiency cooling, as well as heating. As
heat-pump technology has developed, their reliability and popularity
have increased.
Common Types of Air Conditioners
Room air conditioners, also called window units, are small units
that mount into a window frame or a hole cut in a wall (Figure 14).
Room A/C units are designed to cool one room at a time, and multiple
units may be required to cool an entire house. Room A/Cs are a good
choice if you only need to cool one or two rooms regularly, if you live
in an apartment, or if you live in a small, well-insulated home.
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Pros: They’re moderately inexpensive and easy to install, though
some models require special mounting brackets. In most cases, you
can do the installation yourself. They can be less costly to run than
a full-sized central A/C unit if their use is limited.
• Cons: If the unit is not mounted in a wall,
refrigerant lines
you’ll lose the light, view and natural ventilation from the window in which the unit is
mounted. The openings around the unit,
whether it’s mounted in a window or a wall,
must be sealed to prevent air leaks.
blower
Additionally, because the compressor is inteevaporator
grated into the unit, room A/Cs can be fairly
noisy. Also, the thermostat control doesn’t
return
accurately reflect the room temperature, so
grille
manual control is needed to prevent overcooling. Finally, two window units can be
more expensive to operate than an efficient
central air unit.
Figure 15: Central Air Conditioner.
Central air conditioners are larger and have
components both inside and outside the house
(Figure 15). They are permanent home appliances. A central A/C unit
is designed to cool an entire house and often uses the existing heating
duct system to circulate the cooled air. They are advantageous if you
need to cool at least three or four rooms regularly.
fan
compressor
condensor
• Pros: A central A/C is fairly quiet when in use because the
compressor unit is located outside. If you already have a forced air
heating system, you can connect the central A/C unit to the existing
ductwork. They are easy to control with a wall thermostat. You
don’t lose any light or ventilation from your windows.
• Cons: Central A/Cs require installation by a qualified contractor.
Proper sizing is critical. If you don’t already have a forced-air heating
system, ductwork will have to be installed. The existing ductwork
must be properly sized and free of leaks and obstructions for the
system to work efficiently.
Heat pumps are like conventional air conditioners except they also
can provide heat in the winter. There are a variety of types of heat
pump technologies on the market.
Ground-source heat pumps (GSHP) provide cooling, heating
and hot water. GSHP are extremely efficient and have documented
efficiencies up to 400%. That means for every dollar of energy spent,
a GSHP supplies $4 worth of cooling or heating. They have a high
first cost but are extremely durable, if properly installed, require little
maintenance and can last up to 20 years. A GSHP does not burn fuel to
make its heat; rather, it moves heat from the earth into the home in the
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wintertime and from a home into the ground in the summertime.
GSHP are relatively expensive to install, and their payback periods
vary according to local electric costs.
Special features of this model
Room air conditioner
Without reverse cycle
With louvered sides
Manufacturer’s name
Model number
Capacity: 5,450 BTU
Size of models
compared on scale
This model’s efficiency
10.0 EER
▼
Energy efficiency range of all similar models
8.0
Least
Efficient
10.0
Most
Efficient
EER, the Energy Efficiency Ratio is the measure of energy efficiency for
room air conditioners. Only models between 1 and 6000 BTU’s with the
above features are used in this scale.
This model’s yearly operating cost is:
35
Figure 16: Sample EnergyGuide.
EER of
this model
Air-to-air and add-on air-to-air heat pumps are another highefficiency option to consider that is less expensive than ground-source
heat pumps. When added to your present furnace, these heat pumps
can cool your house in the summer and help with the heating load in
the winter. These types of heat pumps collect heat from the house in
the summer and expel it outside. In the winter, the heat pump extracts
heat from outside air and circulates that heat inside the house. These
types of heat pumps work best when the outdoor temperature is above
freezing. Below that temperature, supplementary heat often is needed.
Over the past few years, heat-pump technology has become more reliable, and as a result, a growing number of homeowners in Arkansas
are switching to heat-pump technology to cool and heat their homes.
Bigger Isn’t Necessarily Better
Once you’ve settled on the type of air conditioner you want,
choosing the right size unit for your needs is very important. The size
of most A/C units is measured in terms of BTUs per hour, though
some central A/C units and heat pumps may also be rated for tons of
cooling capacity (a ton is equal to 12,000 BTUs per hour). Air conditioners are designed to cool a fixed amount of space efficiently.
Oversizing a residential A/C system by 50% will cause a 10%
increase in energy consumption. Not only do oversized units consume
more energy, but they also remove less moisture from your home.
The best way to reduce the required amount of cooling capacity,
and the size and cost of the A/C unit needed, is to tighten your home
with caulk and weatherstripping and have it properly insulated. Ask
your heating and cooling contractor to perform a Manual J calculation
to correctly size the system for your home.
Efficient Models Save Money
Along with the type and size, energy efficiency is an important
consideration. Buying an inefficient model will guarantee high electric bills over the unit’s lifetime, which could be many years.
Look for the yellow EnergyGuide label on all new A/C units
(Figure 16). For room air conditioners, these labels display the efficiency rating in terms of the unit’s EER, or Energy Efficiency Ratio.
This is a measurement of the A/C unit’s cooling efficiency based on the
ratio between the cooling output (in BTUs per hour) and the electrical
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power input (watts). Most new room air conditioners have EERs of 9.5
to 10.5. An EER of 11 to 12 represents very high efficiency.
EnergyGuides are useful for general comparison, but note that the
stated energy costs may not accurately represent your energy costs as
your A/C usage and lifestyle and comfort zone may vary.
To further increase energy savings, look for ENERGY STAR®
labeled products.
ENERGY STAR® labeled room air conditioners and central air
conditioners can help save money on utility bills through superior
designs that require less money and energy to keep your home cool
and comfortable.
ENERGY STAR® labeled room air conditioners feature highefficiency compressors, fan motors and heat-transfer surfaces. In an air
conditioner, air is cooled when it passes over refrigerant coils, which
have fins similar to an automobile radiator. The compressor sends
cooled refrigerant through the coils, which draw heat from the air as it
is forced over the coils. By using advanced heat-transfer technologies,
more heat from the air is transferred into the coils than in conventional
models, saving energy required to compress the refrigerant.
ENERGY STAR® labeled room air conditioners must exceed minimum federal standards for energy consumption by at least 10%.
Buy the right size:
Many people buy an air conditioner that is too large for the space,
thinking it will cool better. An oversized air conditioner is actually less
effective than a correctly sized unit and wastes energy at the same time.
Air conditioners remove heat AND humidity from the air. If the unit
is too large, it will cool the room quickly, but remove only a portion of
the humidity. This leaves the room with a damp, clammy feeling. A
properly sized unit will remove humidity effectively as it cools.
Running a smaller unit for a longer time will use less energy to completely condition a room than running a larger unit for a shorter time.
Adjustments to make:
• If the room is heavily shaded, reduce capacity by 10%.
• If the room is very sunny, increase capacity by 10%.
• If more than two people regularly occupy the room, add 600
BTU/hr for each additional person.
• If the unit is for a kitchen, increase capacity by 4,000 BTU/hr.
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Area to be Cooled
(Sq. Ft.)
100 to 150
150 to 250
250 to 300
300 to 350
350 to 400
400 to 450
450 to 550
500 to 700
700 to 1000
Capacity
(Btu/Hr)
5,000
6,000
7,000
8,000
9,000
10,000
12,000
14,000
18,000
ENERGY STAR® estimates that, on average, a properly sized and
installed ENERGY STAR® labeled central air conditioner uses 20%
less electricity than a standard, new, central air conditioner, or about $50
per year or $650 over its lifetime. However, results will vary based on
use and climate, with warmer regions likely realizing greater savings.
Studies show that one-third to one-half of home air-conditioners
don’t work the way they should because they are oversized. Since
energy use creates pollution, by increasing the efficiency of our central air-conditioning units being installed, and by properly sizing our
equipment, we can dramatically reduce energy consumption, reduce
pollution and utility bills.
To find out more about ENERGY STAR® –– labeled products, call
the ENERGY STAR® Hotline toll-free at 1-888-STAR-YES
(1-888-782-7937) or visit http://www.energystar.gov.
What’s a SEER?
The SEER is a central A/C unit’s Seasonal Energy Efficiency
Rating. Unlike the EER, the SEER estimates a unit’s performance over
an entire cooling season, rather than measuring its performance at a
given temperature and humidity level. In short, it measures the seasonal performance of the unit based on the cooling accomplished (in BTUs
of energy) divided by the electricity consumed (in kwh).
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BTUs cooling provided
SEER =
seasonal kwh consumed
A minimum SEER of 10.0 for central air conditioners is
required by the National Appliance Efficiency Standards. There is a
wide selection of units available with SEERs up to 17.
You can save a lot of money and energy by upgrading an older,
less-efficient system. For example, replacing a 1970’s vintage central
air conditioning unit (SEER = 6) with a new unit having a SEER of 12
should cut your air-conditioning costs in half.
Depending on the use, cost of electricity and the temperature, these
savings can actually pay back the cost of a new system within a few
years. In general, central A/C systems are more efficient than room
A/C units. Once again, however, an oversized system will waste
money and energy.
Shopping Tips
It’s a good idea to ask your neighbors and friends with a similar
lifestyle and home style about their systems, how long they’ve had
them and how much they cost to run. Check the consumer review publications at your local library, as well as your local utility, to find the
most energy-efficient models. Then shop around for an air conditioning contractor to install a central A/C system, or a reputable dealer for
a room A/C unit. If you’re having a central system installed, get bids
from three or more contractors and check their references.
Disposal and Recycling of Your Old A/C Unit
In the past, discarded appliances were often dumped in landfills
or even in ditches and creek beds. Very few were recycled and the
hazardous materials in discarded appliances contaminated the soil and
ground water. Today, appliances must be disposed of in accordance
with state and federal guidelines. In particular, refrigerators and air
conditioners require special handling during the disposal process.
This is because the refrigerant used in these older appliances contain CFCs (chlorofluorocarbons). Once released into the atmosphere,
CFCs damage the ozone layer that shields us from the sun’s radiation.
Since 1989, CFCs have been phased out and banned throughout the
industrial world, and all new refrigerators and A/C units must use nonCFC refrigerants.
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Disposing of an air conditioner involves the careful removal of
CFCs by a certified technician. The oil from the compressor crank case
also needs to be removed. The motor and copper tubing can then be
removed for separate recycling. A/C units manufactured before 1978
may have oil-filled capacitors contaminated with toxic PCBs (Polychlorinated biphenyls), a substance now banned in the U.S. These components must be removed and taken to a hazardous-waste facility
before further processing can occur. Finally, there may be temperature
gauges and switches that contain small amounts of mercury, another
extremely toxic substance. Once these hazards are removed, the remaining materials are segregated and recovered according to the recyclability of their materials.
If you have an old A/C system that you want to dispose of safely,
and to properly dispose of any large appliances in Arkansas, check with
your city or county solid waste director or local elected official.
Arrangements can be made to pick up the appliance. This will ensure
that the appliance will be properly recycled.
INFORMATION SOURCES
Energy Efficient Comfort Conditioning Equipment. Florida Solar Energy
Center, Cape Canaveral, Fla., September 1992.
Energy Saving Landscapes: The Minnesota Homeowner’s Guide. Minnesota
Department of Public Service and the Minnesota Department of Natural
Resources, April 1993.
Heede, Richard. Homemade Money: How to Save Energy and Dollars in Your
Home. Rocky Mountain Institute, Snowmass, Colo., 1995, pp. 100-115.
How to Keep Your Cool and Save Cold Cash. Air Conditioning and
Refrigeration Institute, Arlington, Va.
Krigger, John. Residential Energy. U.S. Department of Energy Weatherization Assistance Program and Existing Building Efficiency Research Program,
1994, Oak Ridge National Laboratory, pp. 173-190.
Nadel, Brian. Ozone-Friendly Cooling: A/C Without CFCs. Popular
Science, July 1990, pp. 57-63.
18
Neal, Leon. “Selecting a Central Air Conditioner.” Consumer’s
Research, May 1993, pp. 20-24.
Something Cool You Can Do at Home: Plant a Tree. Midwest Power, Des
Moines, Iowa, January 1994.
Tips for Energy Savers. U.S. Department of Energy, October 1991.
Wilson, Alex and John Morrill. Consumer Guide to Home Energy Saving.
American Council for an Energy Efficient Economy, 1995, pp. 113-142.
ADDITIONAL RESOURCES
•
•
•
U.S. DOE Energy Star: http://www.energystar.gov
ADED Energy Unit: www.1800ARKANSAS.com/energy/
Florida Solar Energy Center: FSEC www.fsec.ucf.edu
This is an Iowa Energy Center publication.
IOWA ENERGY CENTER
2521 ELWOOD DRIVE, SUITE 124
AMES, IOWA 50010-8263
515-294-8819 • FAX 515-294-9912
This publication has been updated and modified for use in Arkansas by the
Arkansas Department of Economic Development – Energy Unit.
ONE CAPITOL MALL
LITTLE ROCK, AR 72201
501-682-7319 • FAX 501-682-2703
WWW.1800ARKANSAS.COM/ENERGY/
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This publication is distributed by:
Arkansas Department of
Economic Development
Energy Unit
One Capitol Mall
Little Rock, AR 72201
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