A consumer purchasing a room air conditioner has a choice of models with various Energy Efficiency Ratings (EER, defined as the ratio of nameplate cooling capacity in Btu/hr and plate power in watts). Models with higher EER's require less energy and are therefore more economical to operate; however, their initial cost is greater. The knowledgeable consumer, interested in making an intelligent purchase decision, will want to make his choice based on a comparison of potential cost savings from reduced energy consumption and added cost for a more efficient model. To do this he needs to have information for calculating the ¢nergy consumption of the unit, and this requires an estimate of the hours of operation to be expected for the geographic location in which the unit is to be installed. In the past, this information has been difficult to obtain. Many articles have been published on the subject of hours of operation of air conditioners, but they have tended to be directed toward central systems, to be based on strictly theoretical calculations, or to involve estimates based on limited, if any, field test data. The ASHRAE 1973 System Handbook, and earlier editions, carried a table in Chapter 43, Energy Estimating Methods, with limited data on estimated hours of operation; the credibility of this data had been questioned in recent years. This chapter has been extensively revised in the 1976 Systems Handbook and now includes a more complete table showing ranges of estimated hours of operation for 36 U.S. Cities; the text notes that "residential units will be towards the lower end of the range".

There has been a strong feeling within the room air conditioner industry that people operate room units in a significantly different manner from central residential systems, and that the annual hours of operation would therefore be different. A need for a study specifically directed toward room air conditioners was indicated.

The discussion which follows will describe the program sponsored by the Association of Home Allpliance Manufacturers (AHAM) which has led to a method for estimating hours of operation for room air conditioners--a method based on correlation with field test data.

The primary intent of the program covered by my paper is to provide a method for an individual to estimate the power consumption of a particular room air conditioner he is considering buying. If the information is to be used to estimate total power consumption of a population of room air conditioners, then something needs to be known about the distribution of power ratings of the units in the population and the hours run for each power rating. We have not gathered any data of this type.