I replaced an 18 Seer, two stage compressor, variable speed fan heat pump system that was 12 years old that had a leaking "A" coil. Since my old system was 12 years old and was an 18 Seer unit I thought I would replace it and spend the extra money to go to a better and Trane's best xv20i seer heat pump system as long as I was replacing the system. I am so disatisfied with this new system and I'm very sorry I purchased it! It too has a variable speed fan but this heat pump has a variable speed compressor as well. I knew this system would run more at lower compressor and fan speeds hopefully using overall less electricity. It does run much more than my old system. The major problem with it running at such low speeds most of the time is the furthest rooms from the air handler are 4 degrees colder in the heating season than the rooms closest to the air handler. You can't speed up the fan because it is controlled by the speed of the compressor. You can reprogram the starting fan speed that is set from the factory at 30% which is their default setting to 40% or 50% starting fan speed. So it was reset to start at 50% fan speed to try and alleviate the problem of the cold rooms. It didn't make any difference in heating those furthest rooms of the house plus it put the compressor into stage 2 heating mode almost immediately which obviously takes more electricity! The compressor regulates the fan speed to its speed. So there is no "FIX" for this! I've also taken the fan control on the thermostat off of "auto" and put it on "Recirculate" which is supposed to even out the temperature in the house. It too didn't help! When there is a heavy demand for heat (which is seldom) and the compressor goes to 100% and the fan does as well those furthest rooms are very close to the temperature of the rest of the rooms in the house. This was close to a $15,000.00 purchase that I feel I am stuck with leaving half of the house uncomfortably colder. I don't know how the air conditioning will be because I purchased this in late fall but I would assume in the summer those furthest rooms from the air handler will be warmer than the rest of the house. In hindsight I should have just replaced the "A" coil in my original unit or buy another two stage system as I had that worked fine saving several thousands of dollars!