Compressors are variable and much more efficient. More efficient and variable speed fan motors along with more efficient blade design. Insulation now is drastically better than glass wool of the past. Electronics are able to be integrated in order to provide more fine grain control and overall design has been improved just due to efficiency standards being placed on a bright yellow sticker. In the past design and component choices never really considered efficiency, while efficiency doesn’t always win out in design choices it’s a weighted factor and influences the overall engineering and design in ways that just didn’t happen before efficiency regulations came about.