The electrical options of your car (rear window defroster, air conditioning, ...) operate thanks to the energy supplied by the motor.
Therefore, don’t use them unless it is really necessary. If the air conditioning is fully engaged, it consumes 20% more energy. In addition, refrigerant fluids used to produce the cold air (presently HFCs - hydrofluorocarbons) are very polluting and are among those responsible for the destruction of the ozone layer. On average, we see a 30% leakage of these fluids each year.
Furthermore, since air conditioning is mainly used when it is very hot, it aggravates the phenomenon of urban pollution. It is advisable to opt for opening the windows or the roof, but you should be aware that this can cause a 5% increase in fuel consumption; however, this is still less than when you use the air conditioner. In order to curtail the use of air conditioning: Park in the shade, if possible. Before starting up the air conditioning system, open the windows in order to let the heat out of the passenger compartment. However, don’t forget to close the windows when you are driving with the air conditioning switched on.
Make sure that the temperature setting is limited to 4 or 5°C below the outside temperature. If it is not too hot, switch off your automatic controls on the conditioner in order to avoid its running constantly once the interior temperature exceeds the setting. If it is very hot, use the setting ‘recirculation’ (in manual air conditioning mode), because by reusing the cool air of the passenger compartment you reduce the energy which the system is using.
Leakage of refrigerant gases is very harmful for the environment. In fact, the leak of one gramme of refrigerant gas is the equivalent of 1,300 g of CO2 released into the atmosphere. When you switch on the air conditioning, you increase your emissions of CO2 by 30 g per km (compared with 176 g/km for a medium range vehicle). This results in an increase of greenhouse gas emissions by 10% to 15% per year.