The prime design difference being the outdoor compressor is separated from the main tank, which is kept on the roof top, there by restricting the hot air blast in the passenger area.
Also that the new unit is more energy efficient as power consumption is less by about 50% and the monthly running cost works out to Rs. 4170/- approx. for three times tank capacity as against Rs. 6200/- for the old cooler , said a Northern Railway release.