Good. Here’s the technical manual for that heat pump:
https://www.alpinehomeair.com/related/Amana%20ASZ16%20Spec%20Sheets.pdfHere’s the relevant section
The furnace is very efficient, with a rated AFUE of 96%.
There’s a couple ways we can drive at this, but to most clearly lay it out lets ask the question: How much money would it cost to get 100,000 BTU’s from each heat source?
Starting with the propane furnace. 1 gallon of propane contains 91,000 BTU’s of energy. To get 100,000 btu’s in your building:
100,000 BTU into building / (96%) = 104,100 BTUs burnt. (1 gallon propane / 91,000 BTUs) = 1.145 gallons. Total cost for 100,000 btus into the building: $1.98.
For the heatpump, this will change depending on the outdoor temperature.
Lets look at the worst case scenario: electric resistance heat (space heaters, heat strips, baseboard heaters)
To get 100,000BTU’s, you would need to consume 29,291 watts, 29.29KW. A cost of $2.49.
Here’s how the COP works with a heat pump. It’s an efficiency ratio. For a heatpump to deliver 100,000 BTU’s, we still need 29.29KW of heat, but we can get some of that from outside the house with the heat pump. So, we don’t have to put in a full 29.29 KW. Using the product documentation, here’s where we get with cost of operation, assuming a 70F indoor temperature:
Outdoor Temp | COP | Cost per 100,000 BTUs |
65 | 4.66 | $0.53 |
55 | 4.30 | $0.58 |
47 | 3.95 | $0.63 |
45 | 3.86 | $0.64 |
40 | 3.65 | $0.68 |
35 | 3.43 | $0.73 |
30 | 3.27 | $0.76 |
25 | 3.08 | $0.81 |
20 | 2.89 | $0.86 |
17 | 2.76 | $0.90 |
15 | 2.68 | $0.93 |
10 | 2.45 | $1.02 |
5 | 2.22 | $1.12 |
0 | 1.97 | $1.26 |
-5 | 1.72 | $1.45 |
-10 | 1.44 | $1.73 |
Therefore, economically, with the cost of energy in your area, your heatpump is always cheaper to operate then propane.
It’s in your best interest to run the heat pump as much as you can, until it becomes cold enough that the heat pump can’t keep up. Only run propane when you are forced to.
However, propane is cheaper then electric resistance heat. Run propane before you run space heaters.