Hi! Last May, I had a 3-ton Trane XL-16i unit installed with electric resistance as the backup heat and a new Trane thermostat (that seems to be set correctly to 3 stage heating/2 stage cooling). This replaced a Trane XE1000 unit of the same size and the same amount of resistance heating. During the summer and fall I noticed that the electric bill was down about 20%-25% when all cooling was needed. As late fall approached and mild heating was needed (never getting off of first stage), the electric usage was still down about 15-20%. But last month and especially this month as temperatures have continued to get colder here in SW Ohio, the electric usage has increased to higher than what the old unit had used. It seems that when this unit is running in second stage for long periods of time, it is definitely less efficient than the old unit. And on days when the auxillary heat is needed some, it gets even worse (which I expect). On a relatively cold day with highs in the 20's and lows in the single digits, energy usage from the heat pump is about 160-170+ KWH per day (and that's with one of the heat banks turned off as recommended by my installer to try to lower energy consumption) while regular day to day usage around the house with appliances, etc adds another 30-35 KWH. During the last 30 days, the average temperature has been 31 degrees and I've used a total of 3,800 KWH. With the old heat pump and a similar average temperature, I was using about 3,000 KWH total. The worst bill with the old heat pump was during a month that had an average temperature of 19 degrees and the total usage then was only 4,400 KWH. If we had a similar month that cold with this heat pump, I would guesstimate that I'd probably use about 5,500-6,000 KWH.
I have the temperature in the house set to 68 degrees. When the temperature drops down into the low to mid 20's, 2nd stage begins to run constantly or almost constantly. Then as the temperature drops down to about 20, I notice that the aux heat will begin to occasionally kick on and off. When it is about freezing out, the output temperature at a register is about 80 degrees on 1st stage and about 84 degrees on 2nd stage. From what I can tell, switching from 1st to 2nd stage adds about 3-4 degrees to the output temperature. Everything appears to be running correctly and the temperature in the house is being maintained.
When the 16i is running 2nd stage constantly, should it be less efficient than my old XE1000 unit? I would have expected a savings every month of the year but the way it's looking, I'll be paying higher electric bills during the colder winter months (probably from December - March) when 2nd and 3rd stage is being used. With a unit that is supposed to be so efficient with heating, I would have expected better. The way it seems, maybe I would have been better off saving money and getting a 14i or 15i. What's nice is that I have until May to decide since the installer I went with has a 1 year money back guarantee. But then the question will come up with what unit I should have installed next.
Is there something wrong that I can check or have my installer check? He was out just last month and said everything looked really good. He ran several tests, including the temperatures and everything was really good including the amount of BTU's being produced.
Any help or advice anyone can provide would be great. Thanks!