Energy Saver on new A/C doesn't work well
I would return it.  

Energy saving modes work like this:
You set the temp and the fan and compressor run until the room is cooled to that temperature +/- a few degrees.  Once the set temperature is reached, the compressor AND fan shut off.  Every 2-5 minutes (each manufacture is different) ONLY the fan will turn on to get the room air circulating though the unit to check the temperature.  If the room got hotter, then the compressor and fan will turn on to cool and turn off when done. Repeat cycle.

Where as the normal mode the fan and compressor come on, and once the temperature is reached, the compressor turns off but the fan stays on continuously.