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相关词典网站：Mr. Electricity is your guide to saving energy in your home.
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39 super tips for saving money on cooling and air
conditioning costs
Last update February 2015
o Links last checked June 2013
In the typical home, air conditioning
uses more electricity than anything else—16% of
total electricity used.& In warmer regions AC can be
60-70% of your summer electric bill, according to Austin
Energy.& This is where the savings are folks, not in
worrying that you left your cell phone charger plugged in too
long.
The easiest way to save is to run the AC less often, and
to dial the temperature up a degree or two when you do run
it.& My tips below show you how to be
comfortable at warmer temperatures.& I use these tips
myself, and as a result I save hundreds of dollars every
summer.& I could take a trip to Las Vegas every year
from what I save by not using AC.& Even if you're
determined to not use your AC any less, we'll cover ways to
keep the heat out of your home, and more efficient air
conditioners, which can still save you money.
Central AC is simply an energy hog.& A window
unit AC uses 500 to 1440 watts, while a 2.5-ton central
system uses about 3500 watts. That's a lot of power.& A
floor fan uses only 100 watts on the highest speed, and
ceiling fans use only 15 to 90 watts depending on speed and
size.
Let me put into perspective how wasteful central AC is:
Watt-hours
per one hour of continuous use
Central AC system (2.5 tons)
Window unit AC, medium size
Refrigerator with door left open
Amount wasted by keeping the fridge door open
Desktop computer system
Refrigerator (normal use)
Ceiling fan (42", on high)
Television (19" CRT)
CFL light bulb (60-watt equivalent)
Leaving your phone charger plugged in
& with phone connected after finished charging
0.3 (too small to represent graphically)
And now, on with the tips!
with less air conditioning
1. Raise the
temperature
2. Install ceiling
fans if you don't have them.
Is raising the thermostat a degree or two really
gonna kill ya?& I don't turn on my AC unless
it's more than 96 degrees outside, and then only if my
computer is running.& Each degree below 78°F will
increase your energy use by 3-4%.& Follow the
other ideas in this section, and you'll feel cooler at
warmer temperatures.& Remember, only losers
set their AC below 80.
Fans can make you feel 3 to 8 degrees cooler,
allowing you to dial your AC to a higher temperature
and still feel just as cool. () &Put
the wind-chill factor to work for you!& And
ceiling fans are cheaper than you might expect: they
start out around $40 at your local home improvement
store, and usually cost less than a penny an hour
to run. (A typical 36" / 48" / 52" ceiling fan uses
about 55 / 75 / 90 watts of electricity respectively at
the top speed.) Central AC costs seventy times
more to run than a fan.
Most people are even able to install the fans
themselves using the instructions provided.& Don't
underestimate
the importance of ceiling fans!
3. Make sure your
ceiling fan is spinning the right way.
Make sure your fan is blowing DOWN, to send air
past your body, removing the hot air that surrounds
your body. If your fan is blowing up, it won't
do any good.& In fact, it's worse than no fan,
because it moves the warm air at the ceiling back down
towards the living area.
(It's true that a fan that blows down also pushes the
warmer air down from the ceiling into the living area,
but it's blowing even warmer air away from your body,
so the overall effect is to cool you down.)
Almost all fans have a switch to change the fan
direction.& It's an up/down or left/right
switch on the side of the fan (between the light and
the fan blades), and it's usually unlabeled.&
Make sure the fan is off (not spinning) before you
flip the switch or you can damage the motor.&
Once you've turned the fan off, it's fine to
physically stop the blades with your hand, just be
gentle so you don't bend the blades, otherwise the fan
will wobble when you turn it back on.& With the
blades stopped, flip the direction (summer/winter)
switch, then turn the fan back on.
do you know which direction is up and which is down?
For most fans, when you're standing under the fan
looking up, counter-clockwise blows down and clockwise
blows up.& Check by standing under the fan when
it's on full-speed.& If you can feel the wind
hitting you hard, then it's blowing down. To verify,
stop the fan, change the direction switch, then turn
the fan on full-blast again and compare the
difference.
4. Use a Bed Fan
5. Use a "Chillow"
pillow
pay to cool the whole house while you're sleeping when
you really need to cool only yourself?& The
Bed Fan solves that problem, running a gentle breeze under
the sheets to keep you cool, so you don't have to
run expensive AC (or so you can dial up the temperature,
which still saves money).& Why didn't someone think
of this before? This could be also great for people who
experience night sweats or hot flashes. And you won't
have to run an expensive AC all night long. .
is a water-filled pillow that keeps your head cool
while you sleep. You can either sleep directly
on it or put it inside a pillow case. I bought one as
soon as it came out and it really works. .
Use cold packs
Wear a
wrung-out shirt
Put these pads in the fridge or
freezer, and then wear them or sit on them (or use
as pillows when you're sleeping).& The cost to
chill them in the fridge is a fraction of what you'll
save by being able to dial your thermostat up a degree
or two.& Check out the
($9) and the
($20+).& Remember, it's cheaper to cool yourself
than the whole house.
You'll probably be surprised at how
well this works.& Afterwards you might wonder
why you didn't try it sooner.& It works even better
if you combine it with a fan.
8. Run around
naked
9. Rinse off in
the shower
Okay, you probably don't want to run around naked,
but wearing lighter clothes will make you cooler.&
Why wear long sleeves and long pants inside the
house?& Wear a t-shirt and shorts and then you
can dial up the thermostat a degree or two.& But
if you do go naked then you'll also save money on
laundry.
A quick, cool shower can keep you cool for quite a
while afterward.& And the water cost is trivial
compared to the electric cost.
Conditioner itself
10. Use an AC
timer or smart thermostat.
For central AC, your thermostat might already
have a timer built-in.& If not, you can replace
your thermostat with a programmable one.
For window unit AC's, many modern units have
a timer built in.& If not, you can use a simple
plug-in timer if your AC has a mechanical On/Off
switch (i.e., you physically move it into a different
position when you turn the AC on).& But plug-in
timers usually don't work if the On/Off switch is
electronic (i.e., you push a soft button on a panel to
turn the AC on or off).
Set your timer or thermostat to turn off about the
time you leave for the day, and to turn back on a half
hour before you get home. Contrary to popular belief,
this does NOT use more electricity than having the AC
constantly maintai it uses less.
You can get programmable thermostats and plug-in
timers from your local home improvement store.
Programmable thermostats come with instructions, but
it's a quick job for an electrician if you're not
comfortable doing the installation yourself. Plug-in
timers for window units start out at $5, and there are
more expensive models with more features.
It's a myth that it takes less energy to run the
AC all day, rather than leaving it off and turning
it on when you get home.& Running the AC
all day when you're away definitely uses more energy,
no question.
The reason is that with the AC constantly running,
it's constantly cooling your home, making it a heat
magnet.& Heat goes to where it's not, so when
your house is cooler, more heat will try to
enter.& So more heat gets into your house, and
the AC has to remove that heat, over and over again.
But if you leave the AC off, then the house will heat
up during the day and then stop heating up.
It's already hot so it's no longer a heat
magnet.& When you get home and turn on the AC,
the AC has less total heat to remove than if it had
been running all day.
Yes, I've tested this, of course.& In my test,
running the AC all day used 317% as much electricity
as waiting until after work to turn it on.& It
was a pretty crude test and I won't be surprised if
the typical penalty is actually much lower, but the
point is, there's definitely a penalty by running the
AC all day.& I hope readers will run their own
tests and let me know the results.
Since this topic garners a lot of interest, I have a
special page all about ?
11. Clean the
filter
12. Replace your
air conditioner
Clean or replace
your AC filter every month.& A dirty filter
makes your AC work harder, which uses more
electricity.& Your home improvement store sells
permanent filters which you can easily rinse off so you
don't have to replace the filter each month.
Before replacing your existing central AC, consider
the alternatives to a traditional AC listed in the
special section below.& They include room-by-room
systems (so you don't have to pay to cool the whole
house if you're using only part of it), whole-house
fans, and geothermal systems.
If you're determined to keep using a traditional AC,
then use an efficient one.& Energy Star models
use 15% less energy than other new models, and up to
30% less than models ten years old. ()
Whatever system you get, look at the energy ratings
(SEER for central systems and the EER rating for
window units). The higher, the better. SEER 13 are 30%
more efficient than SEER 10. ()&
As of 2006, AC's must have a SEER of at least 13,
although they go as high as 19. Both the inside and
outside units should be a similar SEER for best
efficiency. (See
from AC Doctor.)
Whatever you get, make sure your AC is sized
properly. (See next item.)
13. Don't oversize
when buying a new AC
Use the Energy Saver on window units
Most HVAC contractors will try to sell you oversized
equipment, either because they're upselling or because
they're using old-school rules of thumb for sizing
rather than modern load calculations.& Buying a
system bigger than you need is just wasted
money.& My advice:& Many utility companies
will do a "Manual J" load calculation for you for
free.& If yours doesn't, hire an energy auditor
(not an HVAC contractor) so you can trust that the
calculation was done properly.
Here's a , but this could still
lead to oversizing.& The table says I need a 10k
BTU unit for my 406 s.f. loft, but my 7k BTU unit
cools it nicely.
Sizing is a big topic, so I have .
Normally, when the
desired room temperature is reached, the compressor on
the window unit shuts off but the fan keeps going—which
is wasteful.& But many modern window units have an
Energy Saver button that turns the fan off when the
compressor shuts off.
Of course, I got a window unit AC that has just such a
button.& I measured the unit with my Kill-A-Watt
meter and found that the fan alone uses 84 watts.&
If I kept the unit on 24/7, and the compressor ran 50%
of the time, that would be 84 watts x 12 hours/day x
30.5 days/mo. = 30,744 wH, or 30.7 kWh.& But thanks
to the Energy Saver switch, we're not paying to run the
fan gratuitously.& (Though of course, in Mr.
Electricity's household, we don't run the AC 24/7 in the
first place.)
15. Cool your
condenser or window unit
16. Shade your
condenser or window unit
makes your AC run more
efficiently by cooling the condenser with water
vapor as it runs.&& The drier the
environment, the better the performance will be.&
Reviews on Amazon are mixed, some folks raving about
the savings, others worried about corrosion from hard
water.& Me, I'd try it if we had a central
system, but we use window units so we don't have to
cool the whole house. (starting at
$50 from )
Condensors in the shade use up to 10% less
electricity than those in direct sunlight.
17. Don't block
the condenser unit
18. Clean the
condenser/evaporator coils at the begininng of
each season
Tall grass and other debris on or around the
condensor can restrict air flow and use more
electricity.
You can wash the fin coils on the outside with a
garden hose. Unless you know what you're doing, have
the coils on the inside serviced by an AC specialist.
Alternatives
HVAC central air conditioning
19. Alternative
#1: Window Units
20. Alternative
#2: Mini Split System
Central AC is wasteful if you don't use your whole
house all the time.& It's cheaper to cool
just part of your house rather than the whole
thing.& Window unit AC's let you cool just the
rooms you're using, and there are no energy losses
through a duct system.
Don't think you can achieve the same thing by closing
registers in unused rooms.& Doing so promotes
duct leakage which actually winds up costing you more.
()
are neat. You have an outside condenser,
like with a central system, and that runs directly to
a cooling vent in each room -- without any ductwork.
Think of it as a window-unit AC that you mount on the
wall instead of the window, and which is a lot smaller
since the actual cooling apparatus is located outside.
These save a lot of energy compared to central
systems because you cool only the rooms you need to
cool rather than the whole house, and because there
are no energy losses through ductwork in a hot attic.
21. Alternative
#3: Evaporative cooling
22. Alternative
#4: Whole-House Fan
works by blowing water-cooled
air.& It can be a free-standing unit in
your room, or a window-mounted unit, or a whole-house
unit.& Evaporative coolers use a lot less
electricity than an regular air conditioner, and they
work well in dry climates (like Nevada, West Texas,
etc.)—but they don't work in very humid climates at
all.& (Here's a
showing where evaporative coolers work well
and where they don't.)& These coolers use only
about 3 to 15 gallons of water a day, too. ()&
Portable floor-standing units .
A whole-house fan is a large fan that mounts in your
ceiling. It draws in fresh air from open doors or
windows into the attic, where it's then pushed out
through attic vents.& This creates a cool breeze
through your house, and at the same time gets the
super-hot air out of your attic.
Personally, I bought an AirKing
($136) but haven't yet installed
it.& I'll report back here once I have.
Read more about whole-house fans on
23. Alternative
#5: Geothermal systems
Geothermal systems use 30-60% less energy than
typical HVAC systems, run quieter, and require less
maintenance.& They can also heat your
water, too, and in the summer it's free, since the
water is heated with heat that's already been
extracted from the house to keep it cool.
A geo system is a loop of piping under the ground
that circulates water. The heat is extracted from your
home, run through the pipes, and the earth absorbs the
heat from the water.& Basically, the heat is
taken out of your home and put into the earth. This
isn't so different from a traditional AC system, which
extracts the heat from your home and puts it into the
air outside your home.& A geo system is
just a lot more efficient and cheaper to run.&
(See the
which shows how geothermal systems
work.)
Geothermal heat pumps meet the EPA's Energy Star
guidelines if they're labeled at least COP 2.8 for
heating and EER 13 or for cooling.
U.S. homeowners can get
on geothermal systems
through 2016.
In 2006 a geo system cost about $2500 per ton of
capacity to intall. A 3-ton geo system at $7500
compares with $4000 for a traditional system, for a
$3500 up-front premium for the geo system. ()&
A geo system could save in the
neighborhood of $700/yr., paying for itself in less
than six years, not even counting the lower
maintenance costs.& Also, many city and state
governments offer rebates and other incentives for
installing geo systems, making it an even more
attractive deal.& On the other hand, depending on
the geology of your area and the availability of local
contractors, a geo system could cost a lot more than
$2500/ton to install.
I had a hard time finding really good figures to base
my calculations on, but the above should be in the
ballpark.& For AC, I'm figuring 50% savings over
a 3-ton (4200-watt) AC system running 12 hours a day
for five months.& There's also savings on heat,
even if the old heat source was gas or oil, but
heating savings are harder to figure, so I'm
estimating that they'll be a bit below the savings on
cooling. (Here's a cost comparison of
different systems from ,
PDF.)
and Exterior
24. Insulate the
attic
25. Install a
radiant barrier
Poorly insulated attics can lose up to 40% of a
house's cool air. The average home built in
1985-90 has R-11 to R-15 insulation but needs up to
R-49. See the DOE's map for
depending on what part of
the U.S. you live.
Baltimore Gas & Electric says that increasing
the level of insulation from 2-3 inches (R5) to 8
-14 inches (R30) can save $95 to $145 per year for
every 1,200 square feet of ceiling area.
for blown-in attic insulation.
A layer of aluminum foil-type material or
special paint across the underside of the roof in
your attic blocks heat radiated into the roof, and
reduces energy use by 3-8%.
Besides decreasing the amount of attic heat that
radiates into the living space, it might reduce the
heat enough that you could consider turning the
attic space itself into a living space.
26. Test your
ducts for leaks
27. Paint the
exterior with a light color
Austin Energy tested thousands of home duct systems
and found that the average home loses 27% of its
heating or cooling from leaky ducts. ()&
And over 86% of homes had ducts which lost more
than 10%.&(June
2009)& Leaking ducts and insufficient
insulation meant that the average home used 162
kWh/mo. extra electricity per month (July
2009), or 18% more than normal. This is an
extra $233 a year at average electrical
rates.
See if your local utility will perform a free or
rebated duct test, and if not, have an AC
proffesional do it. The money you save by repairing
leaks should easily pay for repair.
Note that those in hot climates like the Southwest
U.S. should use mastic sealant because regular duct
tape will dry out.
The next time you have your home painted, use a
light color, which will reflect more heat than dark
colors.
You might think that by going with a light color you
lose the benefit of the extra heat for winter months,
and so the savings cancel out.& But in reality,
you save much more in summer than you lose in
winter.& The only exception is in frigid
areas where you rarely use air conditioning, and use
heat much more than normal.& See the section
below on white/black roofs for more on this.
28. Install a
metal roof
29. Install a
white roof
Metal roofs reflect much more heat away from your
home than do regular asphalt shingle roofs.& If
you don't like the way metal panels look, there are
newer
that look like attractive wood
shingles.& Another benefit is that metal
roofs are permanent so you never have to
replace your roof again (unlike asphalt shingles,
which must be replaced every 15 years or so and wind
up in the landfill).& I have a home today that
still has the original metal roof installed in 1951,
long before I was even born.
When you replace your roof, metal is best.& If
you don't go with metal, then at least go with
white.& A white roof typically saves 10%, and
up to 20% on cooling costs. (,
)
You might wonder whether your savings with a white
roof in summer are canceled by your losses in winter,
when your roof won't absorb as much heat.& The
answer is that while you do miss out on free winter
heat, the savings in summer are greater than the
winter penalty, in all but the most frigid
areas.&
from the Dept. of Energy shows a net energy
savings from white roofs in even the nothernmost U.S.
states, even after considering the winter
penalty.& A roofer explains in
why the white-roof savings in summer
outweigh the loss of heat in winter.
The U.S. Secretary of Energy has said that if the
world’s 100 largest and hottest cities switched to
white roofs and light-colored cement pavement for
roads, it would be the equivalent of taking all
the world’s automobiles off the road for 11
years. ()
(And yes, I know all about the special tiles that
magically change to white in summer and black in
winter, but until they're commercially available, they
don't do us any good.)
Plant shade trees
Well-positioned shade trees can reduce
indoor temperatures by up to 20 degrees and energy use
by up to 40%.
31. Install an
attic fan?
While a whole-house fan sucks air through your
whole house (see "Alternatives", above), an attic
fan sucks air only through the attic.& Attic
fans aren't usually called for because they don't
give a lot of bang for the buck.& First of all,
if your attic is properly insulated, then the effect
of the fan won't be that great.& (And if your
attic isn't properly insulated, getting
insulation put in is more important than installing
a fan.)
Second, if you normally use air conditioning, then
the fan could actually draw cool air from the living
space into the attic, if your light fixtures, ducts,
and attic access aren't well-sealed.& Third, in
rare cases attic fans could actually backdraft
combustible gases through the house.& And
finally, the electrical cost of running the fan will
likely exceed the energy savings from cooling.&
You could get a solar fan, but in that case the
payback period would likely be a long time.
So if your attic is already properly
insulated, and if you don't use AC or your
attic is very well-sealed from the living space, and
if you don't have gas appliances or aren't
worried about combustible gas, and if you
use a solar-powered fan so you're not paying to run
it, then an attic fan might help, a little.
Austin Energy says reducing the attic temperature
by 10 degrees or more saves up to 10% on AC
costs.& They didn't disclose how much
insulation the attic had though. I'll try to run my
own test if I can ever find the time....
32. Make sure
your doors and windows are well sealed.
33. Use drapes
or blinds to block sunlight
You'll pay a lot more to cool your home when the
cold air easily escapes. Do-it-yourself weather
stripping for doors and caulk for windows is easy to
install, and cheap. Also make sure to caulk around
the holes where pipes go into the wall under sinks.
Also, close the damper to the fireplace when you're
not using it -- otherwise, cool air will escape
through the damper.
Keep direct sunlight out. Direct sunlight can raise
the temperature of a room by 10-20 degrees. The less
heat gets into your home, the less you have to pay
to remove it. Drapes block sunlight and heat better
than blinds.
34. Put solar
screens on the windows
35. Install
reflective film on windows
Solar screening is a special mesh that reflects
much more sunlight than regular screening. It's
available at home improvement stores, and can block
60-70% of the heat from sunlight. Get screens that
don't block too much light, because if your building
gets too dark and you wind up using more lighting
inside as a result (which generates heat) then
you've defeated the purpose of the screens.
Windows let lots of heat into your home, because
they're not nearly as insulated as your walls (if at
all).& Combat that heat infiltration with
reflective film, which reflects 40-60% of the sun's
heat from your windows, and can do so without
blocking the light too, so you can still have nice,
bright rooms.& Film costs about $3-7.50 per
square foot installed, or do-it-your-selfers can get
the material from a home improvement store for about
$1-2 a square foot.& The payback period is 3 to
5 years (or maybe less, if the cost of electricity
continues to rise).& It's critical to use film
that blocks very little light, otherwise you'll run
more lighting inside which will heat up the building
and defeat the point. (more from )
36. Use storm
windows & doors
If you're ambitious, install storm windows and
doors. They can reduce the amount of cooling or
heating lost through single pane glass by 50%.
37. Reduce heat
from lighting
38. Reduce heat
from cooking
Lights create a lot of heat which your AC system has
to remove. Replace your lights with
(CFL) bulbs, which use 75% less
energy and create 70-90% less heat at the same time.
Regular lights give off 10% light and 90% heat, while
CFL's give off 90% light and 10% heat.
In winter months when you're heating your home,
there's no penalty for the extra heat created by your
lighting.& The extra heat created by inefficient
lights means that you pay less to heat your
home.& (In theory there's a difference if
electricity costs much more or much less than heating
fuel in your area, but it's almost never worth
worrying about.)& But while there's no penalty
for using inefficient lights in winter, there's no savings
either.& So with inefficient lights you pay a
heating penalty in summer, and break even in
winter.& And you pay a lighting penalty
for inefficient lights year-round.& So yes, go
with more efficient CFL's or LED's.
Any heat you create from cooking has to be removed by
your AC. Reduce cooking heat by using a microwave
oven. (Microwaves are cheaper to operate than gas or
electric ovens anyway.) Move your gas or electric oven
to be along an exterior wall, if possible.
Miscellaneous
39. Use software
to model your building
Trivia: The EER is the
number of BTU's divided by the number of watts.
BTU's are British Thermal Units, and refer to how
much heat an AC can remove from a room in an hour. A
7000 BTU window unit that uses 655 watts has an EER
of 7000 / 655 = 10.7.& Central AC systems are
so large they're measured in tons instead of
BTU's.& One ton = 12,000 BTU's.
For those who want good data, you can get .
The Fan Switch. Here's how the fan switch on a central AC
system works: If the AC is off, then turning the fan on will
simply recirculate the inside air without cooling it. (It draws
in through the intake and blows out through the ceiling vents as
it normally does.) There's not much advantage to this, because
it doesn't make the house any cooler, but it can help keep the
air "fresh" since it's being drawn through the filter and it's
being moved around a lot.
When the AC is on, the air's already being circulated, so in
that case there's no difference whether the fan switch is on
or off.
The fan by itself doesn't use much energy. It's the cooling
part of the AC system that uses most of the power.
fans cool you
don't make the air cooler! They work by blowing
away the envelope of warm air that surrounds your body.
As a living creature, you generate heat. A lot of it. As that
heat slowly radiates away from your body, it creates a pocket
of hot air that surrounds you. It's like you're being
insulated by an invisible bubble of heat. What fans do is to
push that hot surrounding air out of the way.
This is why blowing on hot food cools it off. It's not that
your breath is especially cool, it's that you're blowing the
heat off the food.
If you're sweating at all then the fan also cools you by
speeding up the evaporation.
So now that you know that fans don't make the air cooler, you
can see that there's no advantage to leaving the fan on when
you leave the room. Fans don't lower the temperature in the
room at all.
By the way, a typical 36" / 48" / 52" ceiling fan uses about
55 / 75 / 90 watts of electricity respectively (less on slower
speeds).
Footnotes:
(1) My 2004 42" Hampton Bay uses 24/28/42 watts on
low/med/high respectively, according to the manual.
On a separate page I have
about how saving
electricity on air conditioning.
Saving Electricity 101:
Mr. Electricity is your guideto saving energy in your home.
Specific Appliances
Environment
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All advice is given in good faith. We're not responsible for any errors or omissions. Elec if you're not competent to work on your electrical wiring then hire a professional to do it.
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