Home Improvement : Adding Extra Cooling Unit Can Save Money

<i> Dulley is a Cincinnati-based engineering consultant</i>

QUESTION: Are there any super high-efficiency window air conditioners made? My family room does not always stay cool. Does it make sense to use a window unit even if I have central air conditioning?

ANSWER: It makes a lot of sense to use a window air conditioner even though you have central air conditioning. It can dramatically lower your summertime electric bills and improve your comfort.

There are some new super energy-efficient window air conditioners available with Energy Efficiency Ratios (EER) as high as 11. They are quiet and have many special convenience features. Many new window air conditioners are significantly more efficient than your present central air conditioner.

Instead of making a major expenditure for a new, more efficient central air conditioner, buying a relatively inexpensive, high-efficiency window or through-the-wall air conditioner is sometimes a better investment. I use a small window unit in the study where I write my column.


If a typical 3-ton (36,000 BTUs per hour) central air conditioner has an EER of eight, it costs about 36 cents (at an electric rate of 8 cents per kilowatt hour) per hour it runs. A super high-efficiency 5,000 BTU-per-hour window unit costs about 4 cents per hour.

By setting your central air conditioner’s thermostat five degrees higher, you can cut your electric bills up to 25%, depending on your climate. Then you can run a small window unit to keep one or two rooms cooler. Since it runs less, your central air conditioner should require fewer service calls.

Super high-efficiency window air conditioners use special coil and fin designs to improve heat transfer and efficiency. Some have special controls to automatically de-ice.

Some models have an energy-saving option that cycles the blower on and off (instead of running continuously.) This is also convenient, especially at night. As your bedroom cools off, the blower stops automatically, so you don’t have to get up to turn it off.


The high-efficiency window units are usually the most quiet too. They are designed with well-insulated large blower compartments. The insulation reduces heat entry and blocks the sound. Rotary compressors contribute to efficiency and quiet operation.

Select a high-efficiency unit with five blower speeds and many adjustable outlet louvers. These features improve the cool air distribution throughout the room or rooms and improve your comfort.

You can write to me for Utility Bills Update No. 396 listing manufacturers, model numbers and EER of the 100 highest-efficiency window air conditioners (12 in each size range) from 5,000 to 14,000 BTU per hour cooling capacity, and a detailed work sheet to determine the proper unit for your home. Please include $1 and a self-addressed business envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.

How to Check for Energy-Saving Glass

Q: I recently had new replacement windows installed and I requested and paid extra for energy-saving low-E (low emissivity) glass. How can I tell if it really is low-E glass and not standard glass?

A: When you are indoors and looking outdoors in the daytime, low-E glass appears perfectly clear. If you stand outdoors and look indoors, low-E glass often has a slight bluish appearance. If some sunlight reflects from it on to a light-colored sidewalk or car, you can sometimes detect the bluish cast. It also looks slightly more reflective when you try to look outdoors at night from a lighted room.