10:29AM | 12/01/07
Member Since: 11/23/07
15 lifetime posts
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.


08:05AM | 12/02/07
Member Since: 11/23/07
15 lifetime posts
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.


05:17PM | 12/02/07
Member Since: 11/23/07
15 lifetime posts
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.


06:16AM | 12/03/07
Member Since: 11/23/07
15 lifetime posts
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.


08:39AM | 12/03/07
Member Since: 11/23/07
15 lifetime posts
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.


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