Concrete pads are not better than plastic pads for air conditioning units. Concrete pads often settle unevenly over time and are more vulnerable to cracking than plastic pads if the pad needs to be leveled in the future.
A concrete pad that settles unevenly causes the air conditioning unit on it to tilt over, according to the Family Handyman. This tilt has the potential to strain the coolant tubes and electrical connections to the air conditioner, resulting in leakage, reduced function and potential damage to the unit. While it is possible to level a tilted air conditioner pad, concrete pads require extra care during the leveling procedure to avoid cracking the pad. Family Handyman recommends replacing existing cracked concrete pads with plastic pads to avoid future issues of this kind.