It is clear that in hot climates, air conditioning will provide considerable benefits, socially and economically, and will be an efficiency factor for the community as a whole. However, most countries in hot climates are developing countries, which cannot provide the high investment and running costs of air conditioning equipment. Those that have financial capabilities, e.g., the Gulf countries in the Middle East, have paid several billions of US dollars in purchasing, operating, and maintaining air conditioning equipment. The magnitude of the expenses may be illustrated by the case of Saudi Arabia, where 45% of the annual 60 billion kWh of electricity is consumed in the air conditioning of buildings. The reduction of this cost will need proper planning. Discusses some factors that are particularly related to hot climates. Appropriate consideration of these factors will reduce the cost of owning and operating air conditioning equipment. These factors are - indoor needs, weather parameters, building materials, and operation and maintenance.

KEYWORDS: air conditioning, deserts, tropics, subtropics, costs, economics, operations, maintenance, buildings, materials, planning, weather, Middle East, developing countries