Home Page > Publications and Reports > Consumer Brochures > 101 Causes of High Electric Bills
Since 1981 the City of Tallahassee's energy auditors have visited more than 40,000
homes. We've learned a lot of ways to help City electric and gas customers save
energy and money. Every year we update this list of 101 problems that cause high
summer utility bills in homes. Here's our list for Summer of 1999.
Any questions? Feel free to call the Energy Services at 891-0020. This is a very
busy phone line so please be patient if we have to take a message and call you back.
We will call back!
- The "FAN" setting is selected at the air conditioner thermostat..........Instead,
it should always be set on "AUTO". Set to cool on FAN, the blower pushes air through
the ductwork continuously while the compressor cycles on and off. Moisture removed
from the air while the compressor runs is reintroduced to the house when the fan
alone runs between compressor cycles. Don't let this happen! Don't set the system
on "FAN"! Set to cool on AUTO, humidity is kept lower, costs are much lower and
comfort is higher. If your ducts are leaky (and most are) the FAN setting is especially
costly to you.
- The air conditioner's air filter is clogged...........Air
flow is restricted. When air flow is restricted your HVAC (Heating, Ventilating
and Air Conditioning ) system runs less efficiently. A clogged filter increases
costs, reduces comfort and can lead to costly equipment failures. When air flow
is severely restricted, ice grows on the air conditioner's evaporator coils, a condition
that can precede "slugging" the compressor with liquid refrigerant. The resulting
repair bill can exceed $1,000. Change the air filter religiously! It should be replaced
monthly during summer and winter periods of heavy use.
- The evaporator coils are clogged with accumulated dust.........Air
flow is restricted. Problems that result are much like those described above for
dirty filters. If you have central air conditioning, all the air in your house draws
through the air conditioner's filter, then through the cooling (evaporator) coils.
Generally the filter doesn't clean the air; its purpose is to protect the equipment,
in particular the cooling coils. In spite of the filter the downstream coils gather
dust and grime over time. Energy efficiency is degraded by about 5% each year as
the coils get dirtier! Your costs go up while comfort goes down. Have a service
technician check the evaporator coils yearly and clean them if necessary.
- The air conditioner thermostat is set too low...........Often
its operation is misunderstood. Your air conditioner runs no faster at a lower setting,
it only runs longer. The recommended summer setting is 78 degrees. Set it 2 to 5
degrees higher when you're away in the day. Recent research in Florida reveals that
home cooling costs increase 12% for each degree setting below 78 degrees. Your
cooling costs can almost double if you set the thermostat at 70 instead of 78 degrees!
- The central heat pump is simultaneously cooling and heating .............and
the cooling cost triples! Overall this is a rare condition, but memorable to
all involved because the summer bills get so stunningly high. A variety of thermostat
and wiring problems can be the cause. For example, we've found situations where
5,000 watts of supplemental heating strips come on whenever the air distribution
fan runs, winter or summer. The auditor detects the problem by running the cooling
system alone (other appliances off at the breaker panel) and timing the meter spin
to calculate power draw. A 5,000 watt overage is readily detected by this method.
- Teenagers...........are full-sized human beings who deserve as much
respect as people of other sizes and ages, even if they use a lot of energy per
capita but don't yet pay the bills themselves. Small children, by contrast, are
low to the floor and relatively comfortable at levels of summer heat that stress
many adults. See #84 below.
- Central heat strips turn on, off, on, off .......even when the hallway
thermostat is set to OFF. With everything in the house off or unplugged and the
water heater switched off at the breaker panel, the meter races, stops, races, stops.
Because of a thermostat, control wiring or other wiring problem, the central electric
heating strips (10,000 to 20,000 watts) are coming on even though the distribution
fan is off and all is silent. Without the fan running, heat from the strips is not
distributed. Heat builds up around the strips until a high-temperature safety switch
is activated, turning them off. They cool. They come on again.........and so on.
Another rare problem like #5 above, but costly when it happens.
- The thermostat is miscalibrated........and so is the thermometer
on the thermostat faceplate. The system cools lower than the temperature selected
by the resident. For example, the thermostat might be set on 78 degrees, but an
accurate thermometer shows that it's actually cooling to 75 degrees. This is an
extremely common situation – We've found thermostats as much as 10 degrees off.
The simplest solution is to rest an accurate thermometer on top of the thermostat,
find out how much it's off, and compensate accordingly when you select the desired
indoor temperature. (By the way, if you'd like to receive a simple card-sized thermometer
that's perfect for this kind of testing, call Energy Services at 891-0020.)
- The customer has a swimming pool........and the pool pump runs 24
hours a day. The high cost of pool pumping is a surprise. Most residential pool
pumps we see are 3/4 horsepower output. Operated all day every summer day, the monthly
energy cost is about $62; operated continuously year around, the annual energy cost
is about $745. A timer for the pool pump is well worth the installation cost, and
usually pays for itself through energy cost savings within three months or less.
The National Spa and Pool Institute recommends that the pool be "turned over" (one
complete circulation of water) once a day. Full turnover of a typical 20,000 gallon
pool, then, requires 4 hours pumping at 85 gallons per minute, 6 hours at 55 gallons
per minute or 8 hours at 40 gallons per minute. Most pool pump systems are sized
to accomplish a full turnover in 4-6 hours. Pumping year around for 6 hours a day
instead of 24 hours a day saves about $558 a year! Installed cost of a timer is
- The ceiling lacks adequate insulation..........Heat from the attic
is conducting through to the house below. Improving ceiling insulation is one of
the best investments you can make towards lowering your air conditioning costs in
summer. If you're not sure what level of insulation you have in your attic, call
us for a free home energy audit. The older your home, the more likely it
is that its original level of insulation would now be considered inadequate. We
still find some older homes with no insulation at all.
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- Humid outdoor air is leaking into the house........through
cracks around doors and windows, electrical outlets, ducts, vents or fireplace dampers
that don't seal tightly. In Florida homes about 38% of the air conditioner's work
(and operating cost) goes to drying out this moist air leaking in from out of doors.
Leaks in the ducts that supply cooled air to rooms will make this situation much
worse, because the overall house air pressure becomes "negative' with respect to
the out of doors whenever the air conditioner is running. In this condition the
house sucks in warm, moist air whenever the air conditioning system runs. The system
runs longer to compensate. Even more warm air is drawn in, which needs to be cooled......and
so forth in a vicious cycle. Costs rise significantly.
- Dogs have pulled air ducts apart beneath the house, cats have bedded
for years in the ceiling insulation, possums have tugged open a crawl way where
water pipes penetrate the floor and they're living in the hollow wall of the bath
tub.........and so forth. Energy wise, the worst of these situations is where
supply or return air ducts are disconnected in the crawl space beneath the house.
Every summer at least one of our auditors reports finding the family dog comfortably
housed in the return air plenum under a customer's house. It costs a lot to cool
- The refrigerator that served for twenty years in the
kitchen still works, and now it's in the garage.........And it's a hot garage.
Those old refrigerators are not very energy efficient, but they sure last a long
time! In a hot garage that old Coldspot may run almost continuously. The new refrigerator
in your kitchen is probably two or three times (or more) as energy efficient, especially
if it was manufactured after January 1, 1993. Energy wise, you're much better off
organizing all your stored foods into the newer refrigerator and unplugging the
old unit. How big a difference in cost can there be? A new, 25 cubic foot high efficiency
refrigerator in the kitchen costs about $5 or $6 a month to operate; an old, inefficient
unit in a hot garage can cost $25 to $50 a month in summer.
- The house is equipped with jalousie or awning windows designed for cross
ventilation.........Instead the house is closed up for air conditioning. Or
almost closed up: Unfortunately, these window types are notoriously leaky. In summer,
the air conditioner must toil to dry as well as cool the air, and major air leaks
cause major cost increases. (See #11 above)
- Hot water leaks.......from a tub or sink faucet. Here's something
we occasionally find: The water heater is located at one end of the house and there's
a leaky tub faucet at the far end of the house. The leaking water feels cold. "Minor
problem", you think. But it could be supplied from the water heater. An easy test:
Tighten down the hot side handle and watch to see if the leak diminishes. Another
test: Put a screwdriver tip to the hot water pipe where it exits the water heater,
and press the handle end against your ear; the sound of running (hot) water is magnified.
A third test: Feel the cold water supply pipe where it enters the water heater;
if no hot water has been used in the previous half hour, the cold pipe should feel
warm (heat from the water heater conducts to that pipe and warms it). If the cold
pipe near the water heater is cold, and no hot water has been used recently, there
may be a hot water leak; cold water is entering the tank (and cooling the inlet
pipe) to make up for hot water being lost to a leak.
- Residents have waterbeds......but are not careful to make them up
each day. That results in significantly increased energy cost! A typical waterbed
costs about $10 a month to heat if it's made up each day with heavy covers that
hold its heat. If left uncovered the heating cost can double. Smaller water beds
cost less to heat than larger: A queen size bed's heating cost is about 22% less
than a king size. Whatever the size, it helps to insulate the bed's edges and bottom
with polyethylene foam, polystyrene foam or even layers of corrugated cardboard.
- A rooftop power ventilating fan pulls hot air from the attic on summer
days.......but a). The fan's thermostatic control is set too low (maybe 95 degrees
instead of 115 degrees), so the fan runs more than it should; b). There's a lot
of air leakage from the house across the ceiling to the attic, or bathroom and dryer
vents open into the attic instead of passing through the roof, so that when the
rooftop fan pulls air from the attic it also pulls air (expensively cooled air)
from the house; and c). The fan motor itself is costly to run, and eats up any potential
savings for having cooled the attic. In general, well insulated attics don't need
power ventilation. Passive ventilation devices such as high ridge, off-ridge, turtle-back
or gable vents, together with low soffit vents, are adequate. The optimum design
is usually a ridge vent (internally baffled so that rain doesn't bounce in) and
- The air conditioning system is not getting enough air
returned from the house......for a variety of reasons. We've seen return air
grills set in the floor that are partly or entirely covered by a rug, for example.
In addition to increasing operating costs, inadequate volume of return air back
to the indoor HVAC coil is a major factor in shortening the life of central air
conditioners. Too little air across the indoor coil can potentially lower the coil
temperature to the point of ice formation on the indoor coil. An air conditioner
with its indoor coil covered with ice is in a "destruction mode" (see #2
- The HVAC filter is located in a return duct plenum under the house.......and
because it's so hard to get to, it's never changed. At some time in the past a plastic
laundry bag was sucked into the return air system and is now plastered against the
filter. Almost every energy auditor can tell of finding situations like this.
- The HVAC air handler, located in a hallway closet, is pulling return
air from the attic as well as the house........adding considerably to costs.
Sometimes this situation is discovered where the resident previously had a gas or
fuel oil furnace in a hallway closet. Originally, the furnace pulled its combustion
air from the attic through an opening in the closet ceiling. When the resident later
switched to a heat pump, the furnace was removed from the closet and replaced with
the heat pump's indoor "blower-coil" unit. But the ceiling opening remained. The
new closet unit was set up to pull return air through a grill in the closet wall
into the closet space, then through a filter mounted in the blower coil unit. But
it's pulling air from the attic as well as the house! Most auditors have a story
of first finding this problem when, with the air conditioner running, they climbed
a ladder, lifted the attic hatch and noticed house air rushing past them into the
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- The air conditioning equipment is inefficient........for a variety
of reasons. First, it may have been inefficient from the start. Equipment ten years
old or older is likely to have an original efficiency rating of 7.5 SEER (Seasonal
Energy Efficiency Ratio) or less. Today, Federal law requires manufacturers to achieve
SEER 10.0 or higher for all split-system units, and SEER 9.7 for package units.
What do these SEER ratings imply? You've probably already guessed: If your cooling
cost is $600 a summer with a SEER 6.0 unit, your cost would be $300 a summer (for
the same amount of cooling) with a SEER 12.0 unit. What other factors affect air
conditioning efficiency? The big three are a). dirty coils, which at normal rates
of dirt accumulation degrade efficiency by 5% each year; b). duct leaks, which in
most Florida homes account for about 20% of air conditioning consumption; and c).
improper charge of refrigerant. How common are these types of problems? In 1988
a widely cited Arizona study of residential air conditioners found the following:
- 75% of the condenser coils were dirty
- 70% of the units had improper refrigerant charge
- 55% of the evaporator coils were dirty
- 45% had dirty blower wheels
- 35% had significant duct leakage
- 10% had a wrong motor or fan installed
- The HVAC refrigerant charge is low.........or it's high. Either
way degrades efficiency. In 1990 a field study of residential central air conditioners
found 27% undercharged and 27% overcharged. Overcharging is worse. The unit's cooling
ability goes down while the power draw goes up: The unit runs longer to do the job,
and costs more per minute to run. Overcharging also stresses the compressor, with
serious consequences for its lifespan. The compressor is the most expensive system
component to replace (see #2 above).
- The air conditioner's compressor runs all the time........whether
the indoor distribution fan runs or not. Rare.
- The outdoor condenser is located beneath a wooden deck........and
air flow is restricted. In summer, whatever heat is removed from the house by the
air conditioning system is released to the outdoors from the condenser unit--that
big metal box in the back yard. Hold your hand in the hot breeze from the propeller
fan--it usually blows upward--and you'll get the idea. To work well it needs plenty
of clearance from decks, bushes and folded lawn chairs. By the way, that hot air
blowing from the outdoor condenser is not hot air from the house. It's outdoor air
heated by passage across the hot condenser coils. The cleaner those coils are, and
the easier it is for the heated air to get away from that unit, the better it works.
Air conditioners and heat pumps only work well if kept clean!
- A resident requires the use of oxygen........and unfortunately,
the energy cost to run these compressor systems is surprisingly high.
- There's a whole lot of cooking going on..........Meanwhile the air
conditioning runs nonstop to cool the kitchen. To avoid this, a lot of folks cook
outside in the summer, eat more fruits and salads, eat later in the evening..........or
use a microwave oven! For the same cooking job, a microwave costs far less than
half as much to operate as a standard electric oven, and doesn't heat the kitchen.
Here's a comparison of costs to cook a meatloaf, from a study by Northeast Utilities
(adjusted to our utility rates):
Electric convection oven
Electric frying pan
Electric toaster oven
Electric microwave oven
- There's a dehumidifier running nonstop, draining through a hose to the
outdoors........and the basement area being "dried" is itself wide open to the
outdoors! Admittedly, this is a rare finding, but let's look a little more closely
at dehumidifiers. They remove water from the air. So does your air conditioner.
But a dehumidifier heats the room in which it sits, just as your refrigerator does!
Nevertheless, for some homes it's a very good weapon in the battle against mildew.
Have you noticed how dehumidifiers all seem to have about the same size pan for
water collection, but have widely different capacities for water removal? The capacities
are usually expressed as pints of water removed in a 24 hour period at some standard
temperature and humidity. A "bigger" dehumidifier, with a larger compressor and
higher operating cost per minute of run time, removes water from the air faster,
but generally less efficiently. If you're catching the water in the pan underneath,
you'll need to empty it more frequently to keep up. If you're draining via a hose,
there's no emptying necessary, but just be sure that the area you're attempting
to dry isn't like the one above, open to the outdoors! That was a real finding by
one of our auditors. The resident was using a high capacity dehumidifier, the room
air was damp as ever and the monthly cost was extraordinary.
- Someone's doing a mighty lot of clothes drying every day..........during
the heat of the day, with a dryer located in an air conditioned utility room, vented
to the outdoors. A clothes dryer has a powerful fan that whips air (house air in
the case above) past the damp clothes at the rate of 150 to 200 cubic feet per minute
(cfm). In a 1,500 square foot house with eight foot ceilings, a 200 cfm dryer can
empty one houseload of air every 60 minutes of operation. In summer, that's a lot
of expensively cooled house air being heated by the dryer and blown out. Just as
bad, that's a lot of lost house air that must be replaced by hot, damp outside air
leaking in fast wherever it can: Through kitchen and bathroom vents, fireplace vents
and dampers, around windows and doors, through recessed ceiling light fixtures,
through electric plug and lightswitch plates, etc. For all the above reasons, it's
best to locate the dryer in an uncooled utility room or garage.
- The water heater's thermostat malfunctions, the tank overheats, tank
pressure builds, the pressure-and-temperature relief valve opens to release a flood
of scalding hot water.............under the house, where no one sees it. An
actual case. Yes, the bills were high! In another similar case, in a student apartment
we found the pressure/temperature relief pipe sending hot water from the under-the-counter
water heater to a connection with the drain pipe beneath the kitchen sink. A steamy
hot mist was rising from the sink drainhole; the utility bill had recently doubled.
In most single family detached homes, the pressure/temperature relief line from
the water heater emerges as a little down-spout low on the back side of the house
or garage. If you find hot water plunging from that spout, call a plumber.
- We experience a dry period, maybe in May or June (like
the severe drought we had last summer).......and water bills rise. It's all
that lawn watering. Home lawns are often over-watered. At normal pressure, a 5/8"
garden hose delivers about 10 gallons per minute. Thirty minutes of unneeded watering
wastes 300 gallons of water! Water waste costs you money and does not improve the
health of your lawn.
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A few tips:
- The best lawn watering time is a windless, morning period. Avoid watering
on windy days.
- Wait longer times between waterings. Grass roots will grow deeper, less
watering will be needed.
- Remove weeds before they get large. They steal precious water from desirable
- Mow regularly, removing only 1/3 of the grass length. Clippings can remain
on the lawn. They help retain moisture.
- The resident's City Energy Loan payment on the utility bill makes the
total bill in summer higher than it was the previous summer........when they
still had their old, inefficient equipment. Ouch. The truth is, new air conditioning
equipment almost never pays for itself through energy savings in less than five
years. Since the term on our Energy Loans is five years, and 95% of our loans are
for HVAC equipment, almost all loan program participants are, on average, saving
less each month than the monthly loan payment amount. (We never represent it otherwise.)
On the other hand, from year six on out, they're doing great. It's been debated
that we might extend our term to seven or ten years. Because the amount of money
we have to work with is limited, it seems best to turn it around in five years and
let more people take advantage of the program. If you'd like to register an opinion
or comment one way or the other about this, call Bob Seaton at 891-6130. We appreciate
- The resident is equipped with a so-called "combination appliance" that
uses a gas water heater to heat the water as well as the house (or apartment).........and
in summer it keeps on sending heat to the house! Rare, but it happens as a result
of failed electronic controls or system valves. Electric and gas costs both increase.
The electric cooling cost typically doubles. For the energy auditor, higher than
expected summer gas cost is often the telling clue.
- Leaky supply or return air plenums.......greatly
increase the cost of air conditioning. Using blower door technology to test Florida
homes for duct leakage, almost all systems are found to be significantly leaky.
The most common sites of leakage are the supply air and return air plenums, which
are the air collecting boxes on the upstream and downstream sides of the blower-coil
unit that distributes air around the house. In the supply plenum, air pressure is
greatest; in the return plenum, air suction is greatest. Any leakage from these
boxes is exaggerated by the extremes of positive or negative air pressure close
to the fan. In the distribution system as a whole, if supply air leakage predominates,
the air pressure in the rooms of the house becomes negative with respect to the
outdoors. If return air leakage predominates, the air pressure in the rooms of the
house becomes positive with respect to the outdoors. A negatively pressured house
sucks in warm, moist outdoor air, burdening the air conditioner; a positively pressured
house pushes out expensively cooled indoor air, losing it to the outdoors.
Usually mere duct tape is inadequate to repair these high pressure plenum leaks--it
simply comes loose. Repairs that last use a gluey paste called mastic, typically
having a high content of embedded fiberglass fabric and high tolerance for variations
- Doors need weather-stripping........to prevent significant air leakage.
The crack around all four edges of a standard door is 20 feet long. If the crack
is 1/12" wide, the total "hole" size is 20 square inches, roughly the equivalent
of a softball sized hole in the door! If the house is negatively pressured whenever
the air conditioner runs because of supply duct leakage (see #33),
that size hole admits a lot of warm, moist air for the air conditioner to cool and
dry. A wide variety of weather-stripping materials are available at local hardware
stores and home supply centers. You'll often find good instructions there too, either
from staff or from how-to booklets.
- Windows and doors need caulking........to prevent air leakage, for
the same reasons discussed above. This is do-it-yourself work. Caulk is cheap, applying
it is easy, but it takes time. Caulk cracks around window and door frames; cracks
where masonry walls meet wood siding or trim; wall penetrations by pipes, meter
box, dryer vent or exhaust vents, etc. Some all-purpose caulks are silicon, silicon-acrylic
and siliconized acrylic latex.
- Gardening and landscaping activities increase water use.......maybe
more than expected. (See #30 above)
- Some of the worst water leaks we find are at toilets...........where
you can lose 100 gallons a day and never know it. Listen carefully for the faint,
high whine of a toilet leak. Find out if tightening the water supply shutoff beneath
the tank will stop the noise. Or, put some food coloring in the toilet tank. If
the color appears in the bowl without flushing, you have a leak. Have you ever seen
a "hung" toilet, where the mechanism catches in mid-flush and water rushes continuously
out the drain? If you ever discover a toilet in your home that occasionally hangs,
don't take chances, have it repaired. One flush uses about 7 gallons of water; a
hung toilet that pours out a gallon every two seconds will lose 43,200 gallons in
a day. Every once in a while a water customer has a toilet hang as they leave for
a weekend...or longer. In just a few days, water loss is in the hundreds of thousands
of gallons. The utility rate for metered water consumption is $1.22 per 1,000 gallons.......For
200,000 gallons: 200 x $1.22 = $244. Don't take chances with a hanging toilet: Costs
can get out of hand in a hurry.
- Windows on the southwest or west side are fully exposed to the setting
sun.......... and they need external and internal shading. In newer Florida
homes sun entering the windows accounts for about 20% of the air conditioning load.
In older homes, it can be as much as 30%. Use of interior shades, drapes or blinds
reduces heat gain across the windows by about 20%. External shade (trees, awnings,
sun screens) works even better. Some newer, high tech windows have special tints
or films that reduce the amount of heat transmitted across the window into the house.
Most window manufacturers now offer high-tech windows with low-E coatings. A low-E
coating is a microscopically thin, virtually invisible, metal or metallic oxide
layer deposited on a window. In a double paned window the coated surface may be
either the outer side of the inner glass or the inner side of the outer glass. In
Florida the latter design works better. The coating acts to suppress radiative heat
movement across the window by reflecting heat back into the home during cold weather
and back to the outdoors during warm weather.
- The refrigerator door won't stay shut............and it's next to
- In some apartments and townhomes, the air conditioner's indoor component
(the blower coil that distributes air to rooms) is located in a small closet, right
over the electric water heater...............which in summer heats the passing
air on its way to the a.c. cooling coils and fan. It helps to lower the water heater's
thermostats to the lowest appropriate temperature (usually 115 degrees, or 125 degrees
if the resident uses a dishwasher) and insulate the water heater.
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- The refrigerator door won't seal when it's shut, the
door is askew or the gasket is damaged..........and cold air is being lost to
the kitchen. Years ago our standard advice was: Properly align the door on its hinges
and/or replace the gasket. Then we learned that replacement gaskets cost $50 to
$80, are hard to find for some older models and are not assured to fit well as replacements.
If your refrigerator is 10 or 15 years old and in poor condition, you're probably
best off to replace it with new one rather than undertake gasket repairs. After
January 1, 1993, new refrigerators are three times (or more) as energy efficient
as similar sized units 10 or 15 years old. A new, 25 cubic foot energy efficient
refrigerator costs $5 or $6 a month to operate. An old one costs three times as
much or more to operate, and may cost much more if it's located in a hot garage
(see #13 above).
- The HVAC system has moisture in the refrigerant........and efficiency
is reduced 5-15%.
- The HVAC system draws warm, moist outdoor air through an unsealed PVC
chase.......that routes refrigerant lines through the slab. Costs rise as the
air conditioner works to cool and dry outdoor air admitted to the system by this
and other routes.
- The electric meter was misread.......high or low. Yes, it happens
rarely. Because the meter registers kilowatt hour usage cumulatively, the billing
self-adjusts the next month, but not without some momentary alarm for those concerned.
- Relatives come to visit in sunny Florida.......and the bill goes
- Kids come home from college.........and the bill goes up.br />
- College students living away from home for the first time move into
an off campus house or apartment in August.........and the first utility bill
has a way of getting high. It seems to relate to that whirlwind of initial activity
that happens to coincide with brutally hot weather: Moving in, cleaning, parties,
friends over, door open, thermostat set too low, etc. (See #99
- Schoolchildren are home from school all summer.........and the bill
- The clothes dryer vents lint onto the air conditioner's outdoor condenser
coils........The system, hampered in its ability to release heat, runs longer
- The dryer vent itself is clogged with lint..........and it takes
longer and longer to dry a load of clothes. With the vent clogged, the clothes get
a hot, damp tumbling, but little moisture is removed.
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- The small pump on a water heating waste heat recovery unit runs nonstop.........whether
the air conditioner is running or not. This can get pretty costly, especially if
the water heater is a long way from the air conditioner's outdoor condenser.
- The water heater thermostats are set too high........and each 10
degrees downward adjustment cuts water heating energy consumption by 13%. We recommend
setting the thermostat(s) at 115-120 degrees. If you use a dishwasher that has no
booster heater, set thermostats at 140 degrees; with a booster, set them at 125
- The air conditioner's outdoor condenser sits baking in the sun........increasing
its operating cost. A north side location for this unit is recommended. It's possible
to shade it with trees, but remember that the condenser needs plenty of "breathing
- The resident has a hot tub.......and unless careful attention is
paid to a tub's cover, insulation and pumping, the added monthly cost can be $20
- The pets have special requirements for cooling.............
- All the lights in the house are on..........or nearly all. In most
homes lighting only accounts for about 6% of the electric cost. The costs can add
up, though, so keep up the habit of turning off lights when you leave a room. If
you have ten 75 watt lights on for twelve hours a day, the cost (at $.0823 per kilowatt
hour) is $.74/day, $22.53/month, $270.35/year. Over 99% of the energy provided to
those lights is converted to heat, less than 1% to light. Remember that
when you're trying to keep cool in summer!
- Outdoor area lights are on all through the day...........because
of a bad photocell.
- There's hot water in the toilet! Six words that mean trouble. For
years we teased one of our energy auditors who insisted he had found this – no one
believed him. Then two others discovered the same thing.
- Vines, bushes, tall grass, leaves, litter or lawn chairs cover the air
conditioner's outdoor condenser unit.........so it can't release heat.
- The house is very large.........and so is the cost
to cool it. There's more volume to heat and cool. Larger homes generally have higher
utility costs, all things considered.
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- The garage was converted to a family room.........without insulating
the walls or ceiling. Now it's the hottest room in the house, and that's where the
TV is located and the family spends the most time. To make it comfortable, the family
turns down the thermostat setting for the whole house. Costs rise. (See
- The family has a refrigerator in the kitchen, an older refrigerator
in the pantry, a freezer in the pantry..........and so forth. Costs rise. If
the newest refrigerator was manufactured after January 1, 1993 it's far, far more
energy efficient than older refrigerators or freezers. Consolidate stored foods
into the newest unit if possible! (See #13 and #41
- The air conditioner is oversized for the house..........so that
it cools powerfully but doesn't run long enough to dry the air. The result is a
cool, damp interior that doesn't feel right. To improve comfort, the resident lowers
the thermostat setting a few degrees and the system runs longer. This dries the
air but overcools it. Costs rise. Everyone should know this about air conditioning:
Bigger isn't better. An oversized air conditioner cycles on-and-off frequently,
removes less moisture and wastes energy. A system correctly sized for your house
will run longer for less cost, dry the air better and give greater comfort than
the next bigger size. Correct sizing is a particular concern in Tallahassee where
we experience a very, very, very damp climate.
- The fireplace damper is open, or there's no damper at all.........admitting
outdoor air or losing indoor air. Costs rise in either case, especially if there
are HVAC duct leaks, and there usually are (see #33 above). One
of our energy auditors took an informal survey of his customers last spring, asking
those with fireplaces whether their dampers are closed. Among those who thought
it was closed, about 50% were wrong: It's open.
- Air conditioning supply registers around the house are closed off...........and
the house becomes negatively pressured with respect to the out of doors, so that
warm, moist outdoor air is pulled in (see #33). Additionally,
airflow across the HVAC evaporator coil is reduced. The system's energy efficiency
and cooling capacity are reduced. That is, for a given amount of cooling work to
be accomplished, the system's running cost per minute and the number of minutes
required both increase. Don't close off vents. Repeat: If you have a central air
conditioner or heat pump, don't close off vents. A lot of older federal
and state energy brochures and booklets have advised closing off vents but now we
know better. Leave ‘em all open.
- Bedrooms or other rooms are closed off, with no way for air supplied
to the rooms to return (as the air conditioner operates)........Each closed-off
room becomes positively pressured while the remainder of the house areas become
negatively pressured with respect to the outdoors. The result is exaggerated leakage
to the outdoors from positively pressured closed rooms, and from the outdoors into
the negatively pressured house areas. Leakage occurs through bathroom vents, fireplace
vents and dampers, around windows and doors, through recessed ceiling light fixtures,
through electric plug and lightswitch plates, etc.
- An air conditioning supply duct leads to the garage..........where
it simply wastes cool air to the "outdoors".
- The air conditioning system's return air grill is set low on a wall
and blocked by a chair, or its set in the floor where it's covered by a rug...........resulting
in restricted return air flow and all the attendant problems (see #2
- A small pool or spa is situated literally inside the house........Rare,
but unforgettable. Why not do this? Because of the phenomenal moisture problems
that result, not to mention high air conditioning costs. Remember, the air conditioner
works to remove moisture as well as remove heat. Even in normal circumstances about
38% of the air conditioner's work (and operating cost) is devoted to moisture removal.
- The customer is attempting to cool the entire house with a variety of
old, inefficient window air conditioners........Here's a topic that deserves
a closer look. Our energy auditors have all observed that customers with window
air conditioners usually have significantly lower bills than those with central
cooling systems. Yes, lower. Why? Because only one or two rooms are being
cooled, not the whole house. However, if four or five old window units are operating
all summer to cool the whole house, then costs get high. Older window units often
have energy efficiency ratings down around 5 EER; newer central systems are at least
twice as energy efficient as that.
Back to TOP
- In the hallway ceiling there's a large whole-house fan with incompletely
closed louvers.............It provides a major site of air leakage to or from
the attic. If you have one of these fans and never use it, you'd do well to seal
it from above and drape it with blankets of insulation.
- The air conditioner's thermostat is near some source
of heat........like a floor lamp. The thermostat gets fooled, it senses heat
and calls for the air conditioner to run.....and run, and run.......Remember, small
thermostat adjustments make a big difference to your cost. If your system cools
to 73 degrees instead of 78, your cooling cost rises about 60%.
- The hallway wall behind the thermostat is hot.......because hot
air is being drawn down from the attic through that wall cavity whenever the air
conditioner runs. This tricks the thermostat into calling for more and more cooling
(compare #72). Finding the pathway of air leakage and sealing
it cures the problem.
- The area where residents sit down to eat is heated by morning or afternoon
sun streaming through a sliding glass door........and the whole house is cooled
to a very low temperature in order to achieve acceptable comfort levels at that
- Old casement or awning style windows are deformed out of alignment and
will not seal shut............allowing warm moist air to leak in, or expensively
cooled air to leak out.
- The house lacks shade on the east or west sides, or a mobile home sits
fully exposed to the sun...........Shade trees can reduce air conditioning costs
by up to 30%, and higher if it's a mobile home.
- Summer maternity............usually brings with it a heightened
concern for thermal comfort. Just ask any woman who's been pregnant through a Tallahassee
summer. Somewhat lower than normal thermostat settings are usually desired.
- Lots of hot water diaper washing..........increases costs for a
period of two or three years.
- A shade tree was removed........and air conditioning costs increased
by up to 30% compared to last year. Shade is important!
- Air conditioning ductwork in a hot attic is poorly insulated.......Attic
heat conducts through to warm the cool stream of duct air.
Back to TOP
- The return air plenum box constructed of sheetrock is uninsulated and
leaky and sits in a hot garage.........A fairly common finding.
- All the components of the air conditioning distribution system, including
the air handler, supply ducts and a long return duct, are located in a hot attic.........Lots
of older homes have their air conditioning systems configured this way.
- Windows lack inside shading devices (shades, drapes or blinds), or the
devices are not consistently operated............These shading devices are tremendously
important. Use them to block heat entry during summer days.
- The resident doesn't pay the utility bill..............Someone else
does, for example a parent. Unfortunately the relationship between this situation
and high bills is consistent.
- A room or wing or extension was added to the house, or a garage or porch
was enclosed.........and the overall cooling costs go up. (See #60
- The air conditioner's thermostat mounted on the hallway wall is not
level.........Behind the thermostat's cover plate its operation usually involves
one or two mercury-containing glass bulbs that tip left or right as the temperature
adjustment lever is moved. When you adjust the lever "downward", calling for cooling,
the bulb tilts and a small blob of mercury rolls over to make an electrical connection.
If the thermostat is off-level the mercury roll-over is affected, and the thermostat's
calibration can be thrown off. For example, maybe you've set the lever to
78 degrees, but because the thermostat isn't level the system cools to 75 degrees.
Cooling costs rise by 15% to 24%. (See #4 above) (Leveling the thermostat
is fairly easy using adjustment screws behind the faceplate, but if you're at all
uncertain about it, have it leveled when your unit is next serviced.)
- Bad meter........Notice how late on the list this one appears. It's
about the last thing an experienced energy auditor suspects to be the problem. How
often is an electric meter too fast? It's hard to pry a definitive statement out
of the folks in the Electric Department's Meter Shop, but not because they have
anything to hide. After a long pause, their answers usually come out like these:
"It's mighty rare". "How often is one fast? One in a million? Maybe one in 100,000?".
"Once in a blue moon". "There was one a while back that was damaged by lightning,
but it was running too slow, not too fast." "Over the past 18 years I can't think
of even one meter that tested fast. We've found some slow, or stopped, but not fast".
The fact is, most meters run very slightly slower as they get older. When a meter
fails, it doesn't speed up, it stops. (By the way this is true for gas and water
meters as well.) Here's what happens when you request an electric meter test: Your
old meter comes off the wall and a new, recently certified-as-accurate meter takes
its place. The old one is returned to the Meter Shop where it's tested by the Electric
Department's meter repair technicians. They bench test it on an RFL 5800 Meter Calibration
System, a $40,000, state-of-the-art "watt-hour comparator". It's no surprise for
older meters to test a shade slow. The old meter is either adjusted and put back
in service, or retired.
- Bathroom power vents are left running...........sending expensively
cooled air to the out of doors. Run these vents only as long as needed to clear
that one room of its moisture. If the bathroom is 10 feet by 12 feet with an 8 foot
ceiling, it holds 960 cubic feet of air. Most bathroom fans remove about 50 cubic
feet of air per minute. In the above example, nineteen minutes of fan operation
sends out one roomful of air.
- The residents left town for a summer vacation and were expecting the
next utility bill to be low........but they left the air conditioner at its
normal thermostat setting during their absence and the weather was hot. For many
folks, the best practice is to set the air conditioner's thermostat up to 83 or
84 degrees when away. The system runs once in a while, preventing indoor humidity
from getting too high.
Back to TOP
- Windows and doors are left open while the air conditioner runs........
- While the family is away during weekdays, a laundry maid or housekeeper
is at work around the house.........and she (or he) sets the thermostat below
- The housecats always nap on a particular spot in the middle of the kitchen
floor..........because a hot water leak beneath the slab is warming that spot
- House type #93 has a package-unit central air conditioner
at one end, supply and return ductwork beneath the house and a garage converted
to an uninsulated TV/family room at the farthest distance from the air conditioner.
A couple of ducts are added to the air distribution system to supply cool air to
the family room.......This is a recipe for high bills in summer, but even higher
in winter. The ductwork has the longest possible run--both ways--to cool the room
that gets the most evening use. The walls and ceiling need insulation. The air conditioner's
delivery fan is probably not powerful enough to handle the additional area, and
the add-on ducts result in an imbalanced system that no longer delivers the requisite
400 cubic feet per minute of air (per ton of cooling capacity) across the air conditioner's
evaporator coils. It all adds up to high cooling and even higher heating costs.
- The air conditioning system is made up of mismatched components........
resulting in greatly lowered operating efficiency. The condenser section and
evaporator section need to be properly matched, as specified by the manufacturer.
- A newly added room is hot so the thermostat setting for the whole house
is lowered........meanwhile, in the attic, the air supply duct to the new room
is laid out and connected to the "boot" above the register, but was never connected
into the main system. By an installation oversight, no air is delivered to the new
room. Surprisingly, most of our energy auditors have found unconnected air ducts
like this at one time or another.
- The ductwork "boots" behind the registers are loose, or ducts have fallen
away from the boots............and the system is cooling the crawlspace under
- Flex duct in the attic is kinked or flattened, diminishing air supply
to particular rooms............and the thermostat setting for the whole house
is lowered to compensate. This kind of problem is especially significant if the
rooms having insufficient air supply are the kitchen or family room. This is a common
- The air delivery system includes some length of panned floor joists
which are leaky.......... The spaces between floor joists are sometimes modified
for use as return ducts. This cavity is made into a duct by attaching sheet metal
over the bottom of the joists and by capping the ends of the joist cavity. A leaky
panned floor joist draws in air from the crawl space or basement. To remedy, seal
using mastic. The ceiling fans run backwards, breezing upwards. They should breeze
downward, so you feel the breeze.
- "The roomate effect"........Happens to college
students in off-campus housing. Each roomate has a different level of thermal comfort
and a different level of concern for energy conservation in general. The energy
practices of the least concerned and least conserving individual often become the
norm for all residents.
- Office in the home......This is becoming more common. Here's the
power draw of some selected home office accessories, taken from a 1993 article in
Power Draw (Watts)
How much this costs depends on activity levels. Suppose the copier, printer and
fax machine are idle 23 hours and active 1 hour each day: Together with computer
and monitor (let's say they are active 24 hours/day), monthly cost is about $15.
- Southeast/southwest sun exposure happens early and late in the air conditioning
season..........Some homes have southern windows that are well shaded by overhangs
through the middle of the summer, when the sun passes overhead, but sunlight (radiant
heat) pours in early and late in the summer when the sun passes lower in the sky.
Air conditioning costs may soar unexpectedly in late September or October, for example.
Typical expression: "It's hotter in here in October than it was in August".
Revised 6/17/99 Energy Services