There are certain factors such as your indoor coil and pump system that affect the efficiency of your air conditioner. If your indoor coil isn’t properly sized to match your outdoor condensing unit, the system may not give you the stated SEER and/or HSPF ratings and could even cause some performance problems.  Not having a variable-speed blower motor means the system will use more electricity because the fan will frequently be operating higher speeds than it needs to in order to move the conditioned air in the house.