The energy class shows how energy-consuming a device is, that is, how much current it consumes. Pursuant to a European Union directive, electrical appliances are required to carry an energy label indicating the class to which they belong.
You can find out about the energy class of the air conditioner you are interested in by looking at the coefficients SEER - for cooling - (Seasonal energy efficiency ratio) and SCOP - for heating - (Seasonal coefficient of performance) in its technical characteristics. Based on the above coefficients, electrical devices are classified in classes from A+++ to G.
Generally speaking, the higher the energy class of a device, the more expensive it is. On the other hand, the higher the efficiency of a device and therefore its class, the less current it consumes. In practice, this means that by buying a higher class device you will reduce your home's heating and cooling costs.
So, the price of class A+++ air conditioners may be quite higher than that of class D air conditioners, but in the long run, you will definitely not regret your choice.