$GDGI Amazingly, at this relatively low temperature, AC units are not very energy efficient. Colorado Springs Utilities estimated that a standard central air conditioning system will use 25% less energy when air temps are at 70° than it does at 95°. Why? All of that hot air cooks the outdoor condensing coils that sit outside of homes and on hot roofs of commercial buildings. The higher the ambient air temp, the harder AC systems must work to keep up with the job of keeping the inside of the building cool.