We had a retrofit GSHP installed back at the end of August 2014 and have been absolutely loving it so far. We switched from natural gas and central AC unit. House was built in 1942, single story 1300 sq feet, unfinished basement with garage at the same level as the basement. Absolutely minimal insulation - we found rotted balsam wool insulation in the part we have redone. The house is super-drafty, so I have been EXTREMELY impressed so far. We are planning to gut the entire house in a couple of years and seal the heck out of everything. System is a 3 ton GeoStar Aston Series 38 with DSH, Intellistart with 1200 feet of horizontal loop bored (not trenched) 15 feet under my backyard. We have about 900-1000 feet from end to end. They also redid all the ducting and even custom made a couple of parts to optimize airflow through the system. Also did all return ducting. The unfinished basement helped tons! We used the cooling a bit in early September and it was outstanding - so quiet and absolutely no bump in our energy bill, unlike when we used the old AC. I am more excited about the heating that it is providing. Not only did we disconnect the gas (saving 25 bucks a month there) but the geo is running so much more efficiently than the old system. I have been tracking our whole house KWH for the past 2-3 weeks during this cold snap and we were averaging about 55-65 whole house when temps were in the 20s and 30s. Now that we are in single digits and teens, we used about 75 KWH yesterday. That is with whole house electric, including water heater, 2 fridges, freezer and a well pump all drawing. I write down KWH each morning when I wake up. Our average non-peak electrical usage ( like May, June) is about 650 KWH with everything but heating/cooling, which is about 25 a day. Means I am heating my home on 50 KWH in an uninsulated home in single digit temps. With 7 cents/KWH during the coldest times of the year, my heating bill will only be $100-$120 or so, total bill less than $200. Its more difficult to beat a natural gas bill, especially in our area, but we seem to be doing it. Our installer told us he could get us 45-55 bucks a month average HVAC bill, and so far we are holding to that. Only difference is he said we'd get that AFTER we insulated, not before. I would bet we are under $1000 HVAC bill this year. Last year our heating bills were nearly $200 for gas, $275 for the entire energy bill each month. Super happy so far and will keep everyone posted on how the system is performing. I am planning to implement a WEL setup sometime next year. So far the system has been running in stage 1 down to about 15 F or so no problem, which is unbelieveable to me. I adjust the swing temp to 1 degree, so it runs for like 6 hours before shutting down. Now that we are getting to single, the last couple nights its been running in stage 2 for about half the time. I have not seen it hit aux power yet, but it could be in the wee hours of the morning. I usually watch it from about 5:30 to 6:15 or so and it has been in stage 1/2. Hasn't been more than 1 degree below the target yet when I wake up!