Cooling Systems
Although your first thought for cooling may be air conditioning, there are many alternatives that provide cooling with less energy use. A combination of proper insulation, energy-efficient windows and doors, daylighting, shading, and ventilation will usually keep homes cool with a low amount of energy use in all but the hottest climates. Although ventilation should be avoided in hot, humid climates, the other approaches can significantly reduce the need to use air conditioning.
Ventilation 
Whether relying on natural ventilation or forcing air through your home with fans, ventilation is the most energy-efficient way to cool your house.
Evaporative Cooling
For homes in dry climates, evaporative cooling or "swamp cooling" provides an experience like air conditioning, but with much lower energy use.
Air Conditioning
Air conditioners range from a small room air conditioner to a large central air conditioning unit. Most air conditioners operate at less than their maximum efficiency, presenting energy-saving opportunities. New air conditioning units are far more efficient than earlier models.
Other Cooling Technologies
Absorption coolers use heat rather than electricity as their energy source, and are now available for large homes. Radiant cooling can be appropriate in arid climates, but is problematic elsewhere. Earth cooling tubes have been installed in a few hundred homes, but the technology is not effective.