Mini Split Air Conditioning Units – Compressor:

The compressor of an air conditioner is key when it comes to energy efficiency. An efficient compressor consumes much less electricity than one that is not. There are different types of compressors: reciprocating compressor: the least efficient, SWING or rotary compressor: efficient Scroll compressor or helical: the most efficient.

Mini Split Air Conditioning Reviews – Inverter Technology.

Technology Conditioners "Inverter" (which regulate the frequency of rotation of the compressor) save energy, avoid peak times and a better fit to the selected temperature. They are available in the market with functionality conditioners "free cooling," which ensures the temperature cooling using outside air when weather conditions permit, represent a source of savings on operating costs.

Shinco Mini Split Aircon – Right Size.

That the air conditioner is older does not guarantee that cool more or better. The devices are too large will cool faster but will not remove moisture. Appropriately sized devices,  eliminate moisture, cooled simultaneously and steadily. Consult your dealer which is the right size, according to the size of your home and its orientation to the sun.
If we want to purchase efficient air conditioner is essential to look at the energy label. As with all appliances, devices with an "A" are the most efficient. In the long run, the more money we have invested in buying what amortize on energy bills.