The absolute best thing you can do to save money on your electric bill, 20%-70%, depending on how dirty the system is, is to have a precision tune-up and professional cleaning done on your system. Most tune-ups only clean the outdoor coils and the cabinets. A true cleaning will clean the indoor coils, if accessible, and the blowers are pulled and cleaned as well as the outdoor coil and cabinet. To find out the truth about saving energy and dollars, you must all so measure the change in performance. Measure before and after, the amperage (how much power you are using), the wet bulb and dry bulb temperatures going in and out of the outdoor coil and the indoor coil. This is the only way to know how many BTUs of heat are being transferred. That will give you the BTUs per Watt, which is the EER of that system at that time, before and after. This is the right way. No one does it better than we do.