36 super tips for saving money on cooling and air conditioning costs

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. If you're serious about saving energy, address your cooling costs first, since that's what uses the most electricity.

Of course, you'll save the most money if you can learn to do without your AC at all. It's definitely possible. I live in Texas and have only rarely used AC. A combination of ceiling fans, insulation, and the other tips below keeps me comfortable -- and saves me hundreds of dollars every summer. I could take a trip to Las Vegas every year from what I save by not using AC.

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 energy. A floor fan uses only 100 watts on the highest speed, and ceiling fans use only 15 to 95 watts depending on speed and size.

Let me put into perspective how wasteful central AC is:

Making do 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 will increase your energy use by 3-4%. Remember, only losers set their AC to less than 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. (NY Times)  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.	So how 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
Most people prefer to sleep with covers, even though that traps the heat your body creates. So you can run an expensive AC to cool the whole house just so you can be comfortable under the covers...or you can simply use a Bed fan. It's a small, gentle fan that operates right under the covers.Why didn't someone think of this before? This could be great for people who experience night sweats or hot flashes. And you won't have to run an expensive AC all night long. Order for $99.95.	The Chillow 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. Order for $30.
6. Wear a wrung-out shirt	7. Shower more
It totally works. It works even better if you combine it with a fan.	A cool shower can keep you cool for quite a while afterward. And the water cost is trivial compared to the electric cost.

The Air Conditioner itself

8. Use an AC timer.
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.  In 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 maintain a cool temperature; 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 leaving the AC on while you're away at work uses less energy than turning it on when you get home. Here's why: Heat goes to where it's not. That's why heat from outside goes into your cooler home. With the AC off, at some point your house will be so hot it can't absorb any more heat. When you come home and turn the AC on, the AC removes all that heat. But if the AC is on when you're gone, then you've turned your house into a heat magnet. But keeping it artificially cool, there's no limit to the amount of heat it can absorb. It can always absorb more heat. And your AC has to remove that heat constantly. Your AC kicks in and removes some of that heat, then the house is cooler so it sucks in more heat from outside, so your AC kicks in again and removes that heat, and so on. This means that throughout the day, your house has absorbed way more than one houseful of heat. And your AC had to remove it all. By contrast, with the AC off all day, then it has to remove just one houseful of heat when you come home and turn it on. Let's say you leave the AC off, and your house absorbs 20k BTU's of heat and then stops, because that's all it can absorb. Now let's say that you have the AC running instead. The house absorbs 5k BTU's of heat, so the AC kicks in and removes it. Then it absorbs another 5k BTU's, and your AC kicks in and removes that. Repeat that process several times during the day. The actual numbers will vary, and I haven't tested this to see exactly how much the penalty for leaving the AC on during the day is, but there is zero question that running the AC all the time uses more energy than turning it on when you get home. This is not a gray area, it's simple physics, and no person with any knowledge of this subject disputes it. Running the AC when you're not home wastes energy, period.
9. Close registers in unused rooms	10. Replace your old AC
If you have central AC you can close registers in rooms you're not using so you're not paying to cool them, but note that if you close too many of them, the pressure in the system could cause leaks in the ducts. Check with an AC professional first to see how many & which registers are safe to close at the same time. Another alternative is to use window units or a mini-split system (covered below) so you can cool only the rooms you need to cool.	According to Austin Energy, today's AC's [2005] use 30-50% less electricity than 15-year-old models. Do consider replacing a central AC unit with any of the alternatives mentioned in the special section below (such as window units or mini-split systems, since then you can cool only what you need to cool rather than the whole house). Whatever system you get, look at the energy ratings (SEER for central systems and the EER rating for window units). The higher, the better. The EER of window units rose 47% from 1972 to 1991. (David Darling) If you replace an old EER 5 unit with a new EER 10 unit, you'll cut your cooling costs in half. As of Jan. 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 more about SEER from Climate Magic.) U.S. homeowners can get a whopping 30% tax credit for installing an EnergyStar-rated AC in 2009 or 2010. Whatever you get, make sure your AC is sized properly. (See next item.)
11. Make sure your AC is sized properly	12. Clean the filter
It is important to use the right size AC, and replacing your old AC with one of the same size is often a mistake. An AC that's too small -or- too big will be inefficient and waste energy. Here are AC sizing calculators for window units and central HVAC systems. A properly-sized AC will run 15-30 minutes per hour when the outside temperature is 85-90°F, and almost constantly when the outside temp is above 95°. (source)  Here's a good story about improper sizing.	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 wash with a garden hose so you don't have to replace the filter each month.

The Condensor

13. Cool your condenser or window unit	14. Shade your condenser or window unit
An AC Mister makes your AC run more efficiently by cooling the condenser with water vapor as it runs. Evaporative cooling is an old concept so I have no doubt that it works, but I haven't tested this product so I can't say how well it works. The drier the environment, the better the performance will be. (starting at $50 from AC Mister and Cool-N-Save)	Condensors in the shade use up to 10% less electricity than those in direct sunlight.
15. Don't block the condenser unit	16. 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 to HVAC central air conditioning

17. Alternative #1: Window Units	18. Alternative #2: Mini Split System
Central AC is wasteful because you always have to cool the whole house, rather than just the parts of it you're using. There's also energy losses through ductwork running through a hot attic -- especially if your ducts aren't perfect. Window unit AC's let you cool just the rooms you're using, and there are no energy losses through a duct system.	Mini-split systems 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.
19. Alternative #3: Evaporative cooling	20. Alternative #4: Whole-House Fan
An evaporative cooler is a big box fan that blows water-cooled air. It can be either free-standing in your room, or it can sit outside the house and blow the cooled air in through a window. 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 map showing cooler effectiveness by region. Be aware that they use a lot of water -- 66 gallons a day according to the average in one study. (visit an evaporative cooler store...)	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. Even better than a traditional whole-house fan is one that combines evaporative cooling by misting an intake vent, as with the EnviroCool. Read more about whole-house fans on Wikipedia or AtticFans.com.
21. 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. 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.	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. (EPA) 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 GeoExchange.org, PDF.) More from: Ask the Builder Geothermal Heat Pump Consortium

Reducing Heat

34. Reduce heat from lighting

35. Reduce heat from cooking

Lights create a lot of heat which your AC system has to remove. Replace your lights with compact fluorescent (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. Whatever kind of lighting you have, turn it off when you're not using it. It's not just using electricity, it's adding heat. (But don't try to heat your home with lights in the winter, either; lighting is an inefficient way to generate heat.)

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

36. 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 software to calculate the heat gain and heat loss in your home or business.

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.

How ceiling fans cool you

Fans 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).

On a separate page I have questions I've received and answered about how saving electricity on air conditioning.