With your rates. And using the temps you posted.
Making a WAG, A duel fuel should save you better then 24%, providing your thermal balance point is 30°F.(Thats 24% for that system, not total of both systems).
Thermal balance point is the outdoor temp at which your heat pump can no longer heat the house by itself.
And with those cheap gas rates. If you use set back. It won't cost you an arm and a leg to use the gas heat to recover.
So the savings is a little better than what we originally thought. So it seems to me that if I knew I would be here for 20 years, the dual fuel would be the way to go. Otherwise, it really comes down to whether I want protection from potential rising utility costs. Would you agree?
I just found out that our electric provider has a rebate program for heat pumps (not dual fuel). It is $300. In addition, I would have to participate in a load management program for 5 years where they have 25% control over the ac and heat strips. This would also allow me to get a 10/month credit on our electric bill for 4-5 months during the winter, and a $4/month credit in the summer. Is this worth considering?
Until you and the Ms. want to wrap Christmas presents in July and they shut down air conditoner at 3:00 in the afternoon.
They told me that at 25% control the difference isn't very noticeable. Whether that is really true or not, who knows. I guess it is something to consider. I imagine it depends on what temp you like your house set at. Our tstat is no lower than 77 in the summer.
Here in the Sunshine State when our provider F.P.L. turns off (demand side management) the air conditioning we get service calls. I'm not sure how they would control 25% of the a/c maybe someone else knows.
You should see weather dual fuel or electric aux saves you more in operating cost. And then see if the rebate, and load control save you more, and are worth the inconvience, of having a hot/warm house in the summer, and a cold/cooler house in the winter.
An accurate load calc is the easiest way for a contractor.
If you want to figure it out yourself.
Trail an error.
The simple way. Set the lock out to 30°. If it can't heat your house at 35, you know to raise it. If it is still heating the house at 30, lower it 5°. Repeat process until you find the balance point.