How do I figure which is cheaper to run, HP or NG

[Bentonville]

I am now trying to learn about my new 4 ton Dual Fuel Trane system. I have posted a couple of questions and the people here are very helpful.
Now I am trying to get a fairly accurate idea of which is cheaper to run, the Heat Pump or Natural Gas.
I don't know how to estimate even though I know how many therms I used for heating with an old Comfort Maker last December. I paid bout 98 cents per therm. I paid .11 cents per killowatt hour. I don't know how many the new system uses of either fuel. I live in eastern NC.
Which is cheaper? If I converted therms to Killowatts and paid .11, the bill would be three times the electric bill. Is there a way to anticipate the expense of running my system?

[garya505]

1. Go to:
http://championknoxville.com/default.aspx

2. CLick on the link "IC HVAC Equipment Cost of Operation" on the left side of the page, about 3/4 of the way down the page.

3. Select the "Dual Fuel" tab.

[Bentonville]

That is just the ticket. Now I can see that having my system on the unrestricted mode will do just fine here. Most folks have their system set at 35 or 40 outdoor sensor. That will not save as much as letting the HP work down to about 25 if it will do the job. In unrestricted mode the furnace will take over before that point, probably. I had my system wired for both. The thermostat has to be reprogrammed for the outdoor sensor but I can see the temp. outside now. I can easily have it changed to the outdoor sensor if I see I am spending too much money.
Thank you very much. What a great forum!!

[HVACTechNC]

Double check your numbers bro. I just did it with the information you provided and I came up with 20 degrees F as the balance point between the heat pump and furnace. Since Progress Energy and PSNC don't change their rates all that frequently I would set the thermostat to control changeover at 20 degrees and be done with it.

[Bentonville]

I was using the program on the website and put in the price per therm ast 93 cents. I put 11 cents per kwh. The time was 720 for thirty days and the BTU was 60.000 although my machine is 72500. Perhaps I did something wrong. Anyway...I had them hook up the sensor on the north side of the house. If my gas and electric are really high this winter, I will use the restricted mode. I am thinking with the unrestricted mode the switch over temp. will be lower than setting it at 35 like all of my neighbors with Tranes. Thank you a lot. I believe our climate is almost identical. Hot and humid in the summer and cool to moderate cold in the winter except for probably a week of teens and twentys, usually. I love the AC on this system. It is way more even throuout this house than the old Comfort Maker with a 10 SEER and one speed fan. My wife says it's the first time in the twenty six years we have lived here that she has actually been comfortable. Next is to get some more insulation blown into the attic. I have 14 inches but it's settled over the past 18 years. I know, I should have done that first but the AC just died on us so I had to do something. We went a month without it in those hot days of early June. Reminded me of my childhood when we did not have AC at all, even in the cars.
Thanks again. I never knew how complicated HVAC was. Those guys really earn their money. My installer has a place at the beach. I can't afford to rent a room for a week at the beach. I went into the wrong profession (teaching). Still, there's a lot to know and some difficult crawling and such. More power to you and those in the profession.