This is a common question and one that is likely to dominate the air conditioning industry for the next few years.
Here is an explanation of the difference:
Non-Inverter or Fixed Speed:
A non-inverter is a basic model which operates at a fixed speed, simply controlling temperature by switching on/off alternately. These are significantly cheaper to buy but consume up to 40% more electricity, because of this fluctuation. The below illustration will give you a good idea, of how this work:
An Inverter has a variable-speed compressor which constantly regulates to the desired temperature – a more economic method of operation and A-graded for energy-efficiency. Although costing more to buy, inverters offer a wise long-term investment. Such as the below illustration:
In conclusion, we always advise clients that an inverter is always a good option.
However, this does has a cost downside, as these units as usually more expensive and the energy saving on just one unit is minimal when compared to fixed speed units.
Fixed speed unit have become more energy efficient and we advise that if you are installing less than 5 units into a building, then the cost saving would be minimal.