When you shop for an air conditioner next summer, check the yellow label. The cheapest unit may be no bargain if it costs more to operate.

The Federal Trade Commission moved ahead yesterday on regulations to require appliance manufacturers to put labels on their products disclosing the annual energy cost of operating the units.

Congress ordered the commission in 1975 to develop energy-cost labels for 13 appliance categories. Yesterday the commission approved staff proposals and released the sample labels for public comment.

FTC officials said they expect the yellow energy labels to be in stores next summer.

Chairman Michael Partichuck said the labels would help consumers buy "energy-efficient appliances that cost them less over the long run."

A product that costs more initially might be cheaper to operate and thus be cheaper over time. Shoppers will be able to compare energy costs as well as price tags.

Appliances to be labeled are refrigerators, freezers, air conditioners, washers, dryers, dishwaters, furnaces and other heating equipment, televisions, humidifiers and dehumidifiers, water heaters and ovens.

Each label will:

Identify the product.

Provide an estimated yearly cost for operating the model based on average use and utility costs.

Give the range of energy costs for similar models.

Provide a table to help estimate more accurately what a consumer will have to pay to operate the unit based on local utility costs and an individual's pattern of use.

Manufacturers will be required to test appliances annually to ensure that information is current. An estimated 10,000 appliance models will be affected by the labeling requirements.