Firstly the US7 and other AC units can't really be compared one-for-one on efficiency alone.  Most AC units are forced air heating devices while the Daikin US7 is a comfort solution. That's what sets it apart from all others along with being the lowest cost to run / lowest energy consuming air conditioner / heat pump on the market.

The reason it's so much better for comfort is that it includes a built in humidifcation unit valued at $500-1000 which harvests moisture from the outside air.

Efficient and cheap to run 

The US7 heater air-conditioner is more than 600% efficient compared to direct electric systems and more than 900% efficient when compared to average existing gas ducted systems.  To put it in different terms the unit uses 1/6 the energy of a conventional electric resistive heater and 1/9th the energy of an average existing gas ducted heating system to provide the same amount of heat to your home.

To ensure you aren't under sizing or over sizing your Daikin US7, we generally like to get an idea of: