I recently had this unit installed in my passive-solar house. My cooling load is bigger than my heating load, due to passive solar gains, so my installer recommended 1000 feet of vertical loop. I have only had it for 2 months and it hasn't been the hottest summer ever, but I thought I'd post what I have seen so far. I am not in need of instant cold or heat, so although the TT30 has 2 stages of cool and 2 stages of heat (3 with aux) I set up the ecobee to only use stage 1 for now, which makes the 4-ton unit run roughly as a 3 ton unit. I find the cool air put out by the field to be so cold (around 55deg) that I can feel the dropped temps in the hosue within a half hour. As an example, last night the house was 80deg which is fairly hot. The system including the fan had been off the entire day. I turned the unit on at stage 1, and it reached the 75 deg setpoint in 90 minutes. The fan was set to run throughout the night and the unit never kicked on again, as the temps were fairly low outside (around 70deg). At the time the house reached 75deg, the water in temp had risen to 65deg fwiw. For me, this is perfect for deciding whether or not to even turn the unit on. Some people are looking for faster cooling (using stage 2 for, example) or needing to come home to a house that is already cool (setting the thermostat to turn on an hour earlier, for example) but with a unit running this quickly, I feel like I can save energy by just turning it on when needed, checking the outside temps and humidity, and make a game-time decision, rather than running it when not needed, or running it just because the program says to. The air conditioner it replaced (3 ton) took much longer to get the house temps and humidity down, and a very long time to even feel like it was running. But so far my electric bills have been lower, and the cooling performance much higher. I am not sure if I will see the same performance in the dead of winter, but I am anxious to find out.