Hope some one can answer this.
I've figured out how to compare the cost per BTU of propane versus electrical heat.
Now for the heat pump. The best I can find has to do with the coefficient of performance (COP). I've found a statement that todays heat pumps have a COP between 2 and 5.
Is it correct to understand then that for each BTU of electricity that goes into a heat pump, it puts out twice as many BTU if it is rated as a COP of 2, three as many if COP of 3 etc.?
Help me understand this.
I understand the SEER rating part.

Yes. A COP translates to the amount, so 2 is intended to mean twice as much heat from one unit of electricity. Most air heat pumps provide that. Ground source heat pumps can reach 5.

http://www.canren.gc.ca/prod_serv/index.asp?CaId=169&PgId=1023

www.heatpro.us energy businessmen's knowledge

Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

Then my next question is:
If my propane cost $22.40 per million btu (at 91500 btu per gal, cost of $2.05/gal) and my electricity cost $35.50 per million btu (3,414btu/kw at cost of .1214099/) then divide the cost of elect by 2 as the heat pump gives me 2 times the btu per btu consumed, then my elect cost drops to $17.75 per million btu released or removed from/into the house. Assuming the inside unit is 100 percent efficient.
Somewhere in there, it must be something having to do with the outside temperature.
Where am I off on this?
Don't take it that I am arguing on this. I am trying to understand something I know very little about.

Yes, propane is often more costly than even resistance electric in many areas, so a heat pump can save as long as installation is done with sealed ducts of the right size and good insulation.
http://www.heatpro.us/duct/ductloss.html

COP does have a relationship to air temperature. As air temperature is different north and south over the year, there is no one answer that is unrelated to air temperature. However, in the north, even with sub-freezing temperatures for some months, a heat pump will provide a COP of 2 when done right.

www.heatpro.us energy businessmen's knowledge

Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

I guess my basic question is: If propane cost 2.05/gal and electricity cost .1214099/kw, then which is going to be the cheapest way to heat my house this winter?
The propane is used in a none-externally vented heater( I know your opinions regarding these) and the electricity I use is in a heat pump with a SEER of 13.
I haven't figured out a way to compute the comparison.

Propane has 93,000 btu/gal.
It will burn with at least 80% efficiency. .8 x 93000 - 75,000 btuh

Electricity has 3413 but/kw

There are then 75000 divided by 3413
equals 22 kw in a gallon of propane.
22 kw times .12 = $2.61
Propane is $2.05 gallon

A heat pump will usually give
a COP of at least 2. The heat pump will give 2 btuh per invested 1 btu of electric.
A heat pump will provide 75000 btuh at a cost of 1/2 of 2.61 = $1.30

www.heatpro.us energy businessmen's knowledge

Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

Ok, I think that even I can understand that.
For the same amount of heat it is costing me $2.05 if supplied by propane and $1.30 if provided by electricity.
One last question and I'll leave you alone.
I've read that propane burns/delivers its' Btuh at 99.9 % efficiency (if not vented as in my case). If I substitute that into the calculation, it gives me a cost comparison of $3.27 divided by 2 or $1.63 (25% more economical) for the electricity. Which is still much in favor of the heat pump/electric set up (as long as the resister strips don't cut in).
If the above is correct in your opinion, no need to answer. Thanks much for the assistance.

Almost.
Even with the electric strips kicking in, in northern climates, the heat pump delivery of heat is 2 to 1 of electric resistance. If the elements don't kick in as in the warmer South, even better, about 3 to 1.

Although you gain about 20% efficiency by having no vent, the reasons that people vent furnaces to the outside, as the efficiency of the vented and non-vented combustion is the same, is the clue not to breathe the products of combustion. Non-vented heaters stray from safe in time as do all combustion devices.

www.heatpro.us energy businessmen's knowledge

Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

Thanks. You almost dazzled me with your foot work when you said:"the efficiency of the vented and non-vented combustion is the same".
But I thought for a while. Yes, the combustion (freeing the Btuhs) is the same. The furnace efficiency is how much of that is sent into the house vs how much is released up the flue/vent/.
As for the dangers of the non-vented burners--I've lived dangerously on the edge all of my life. Why, I even drove on the interstate in Dallas/Fort Worth at go to work and go home times!!! Talk about placing your life in danger!!!!
Thanks for all the help. I've learned much from our discussion.