It is highly recommended to have a maintenance program for your air conditioning units, either on a specific period or a 12-month basis, to maintain the equipment warranty, lengthen the operational life of the equipment, keep the system energy-efficient to reduce running costs, and avoid intermediate call-outs. Every unit comes with a warranty of three, five or seven years, depending on the manufacturer and AC type; however, without a maintenance contract, the warranty will be void. The exact number of maintenance inspections depends on the AC unit type and the local environment, but typically it is two to four per year, and sometimes more are required. During inspections, the engineers will perform multiple checks, such as cooling and heating efficiencies, cleaning internal filters, and verifying all AC operations.