Air Conditioners

I live in the valley during the winter, and I close my home for six months a year. Can I turn my air conditioner off when I leave or should I leave my air conditioner on during that time?
There is no scientifically documented "correct" answer for this question. Some customers are satisfied with turning the air conditioner off, others set it at 85 or 90 degrees.

Is it more energy efficient to keep my home at one temperature (set it for 79 and leave it), or is it better to turn my air conditioner up a few degrees at night to 84 and then down again the next day when the sun starts hitting the house?
By setting the temperature up 5 degrees for 8 hours a day, the typical home can save $3-$5 a month. The exceptions are those homes that are on the Demand Advantage or Combined Advantage rate plans. Both rate plans have a demand component that charges a higher price for the most electricity used in a 60 minute period.

Setting your temperature up, then down again may cause the air conditioner to run for a full 60 minutes, setting a high demand. The cost of the high demand may offset any savings from turning the temperature up.

Is it better to leave the air conditioner fan running all the time, or should I set it on auto on and off?
If you want the most economical operation, set it on auto. If you want a stable, more even temperature and more comfort, set it on run.

Leaving the fan to run all the time mixes the air better and maintains a more even temperature throughout the house, but it costs more. If you can set the temperature up two degrees with the fan running all the time it's about a break even on the cost compared to running it on auto at two degrees cooler. If you have ceiling fans, you can get the same effect for less money by using them to distribute the air and running the air conditioner on auto.

Where do I need to set the thermostat on my air conditioner to get the best value for my money? I have been told 80, 79, 78, etc.
The higher you set your thermostat, the less it will cost to cool your home. We recommend setting your thermostat at 79 degrees when you are home and at 85 degree when you are away. For every degree you raise your thermostat above 80 you will save approximately 2 - 3 percent on the cooling portion of your bill. The determining factor is the value you place on being comfortable. Some people prefer to be comfortable, no matter what the cost. Others prefer to save money over comfort.

One way to save energy and remain comfortable is to use ceiling fans. Ceiling fans create a “wind chill” effect that can make you feel up to five degrees cooler. However, unless you set your thermostat temperature higher, fans will not save you money. You should turn off fans when you leave the room. Ceiling fans do not reduce the temperature in the room. They merely circulate air, making you feel cooler.

I have a 2,050 square-foot home that was built 10 years ago. The house is fairly efficient but I'm thinking of upgrading my air conditioning unit because the compressor rattles when it shuts off. Have there been sufficient technological advancements in the past 10 years for me to notice a difference on my monthly bill if I have a new unit installed?
In 2006 the minimum efficiency allowed by law increased from 12 SEER to 13 SEER*. Air conditioners and heat pumps are available with SEER ratings of up to 20. Your 10 year old unit was probably a 10 SEER when it was installed. By improving to the new minimum of 13 SEER you can expect to save 15 to 30 percent of your cooling cost, or $90 to $180 per year for a typical Phoenix area home. If you upgrade to an 18 SEER the savings will be 38 to 50 percent, or $228 to $300 per year.

* SEER = Seasonal Energy Efficiency Ratio, the common measure of air conditioner efficiency. The higher the number, the less energy is used.

The lights in my home dim when my cooling unit turns on.  Does this mean there is a problem with my unit or my breaker panel? Air conditioners, refrigerators, freezers, furnaces and other devices that have large motors require large amounts of power when the motor first starts. Once the motor is spinning, the energy requirement drops down.

This instantaneous need for motor shaft speed can cause a momentary dimming of your lights. AC units come equipped with start-up capacitors. These give the motor an electric boost when it first starts up. But over time, these capacitors can get weak and become ineffective. Eventually the power draw can cause circuit breakers protecting the wiring to the units to trip.

Your air conditioning system may also be overcharged with refrigerant. Overcharging puts stress on the compressor, and in turn the motor, when it tries to get the compressor engine moving. 

Excessive dimming can also be caused by a loose neutral wire in the breaker box. Your AC serviceman can check for overcharging of your AC unit, properly working start-up capacitors and loose neutral wire connections. If you need an AC contractor reference, contact the Arizona Heat Pump Council for an APS Qualified Contractor referral at (602) 371-3636, or (888) 890-9730 outside the Phoenix area.

When is the best time to have my cooling and heating system checked? Do you have a list of recommended service people?
It is generally best to have your cooling and heating system checked in the spring, prior to the start of the heavy cooling season. If you have it checked before the cooling season starts, you can usually get more timely service and may also get a break on the price because spring is generally a slow time for air conditioning contractors. However, if your cooling and heating system doesn't seem to be working properly, or if it's making strange noises, have it checked immediately.

APS works with a group of independent businesses we refer to as APS Qualified Contractors. They receive special training sponsored by APS and are required to be licensed, bonded, insured and to maintain a good business record. An APS agent follows up on each call to see that customers are satisfied. If there is a problem, the agent follows up with the contractor to mediate a solution.

For a referral to an APS Qualified Contractor, call (602) 371-3636 in the Phoenix area, or (888) 890-9730.

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