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Heating Cost Comparison


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A friend asked the other day about heating efficiency of electric versus propane.  I thought the attached Heating Cost Comparison spreadsheet may be useful to others.  Your cost of fuel and system efficiencies may be different, so you'll want to update those cells for your use.

For my engineering friends, I did take some liberty giving heat pumps an efficiency rating.  Obviously a system can't be more than 100% efficient.  Heat pumps are typically rated in Coefficient of Performance (COP) units which in my example would have a COP of 2.4 or with great liberty 240%.

Heating Cost Comparison.xlsx

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4 hours ago, Jim & Wilma said:

Heat pumps are typically rated in Coefficient of Performance (COP) units which in my example would have a COP of 2.4 or with great liberty 240%.

As a clarification, the COP of a heat pump will decrease as the outside temperature (thermal reservoir) falls and will reach 1.0 at roughly zero degrees F.  However, as the temperature falls below 32F water vapor condensing out of the air will form ice on the outside coils and it will be necessary for the device to "reverse" itself to melt the accumulation or to derate itself. 

I believe some (all?) Dometic heat pumps reverse themselves like residential systems.  From what I've read my new Coleman Mach8+ heat pumps derate themselves in some manner at temps below 40F.

One thing that varies among heat pumps is the indoor coil temperature. A long time ago we had a residential heat pump which produced air on the indoor coil that felt cool to the touch (it was below skin temperature).  It was dreadful.  Our new Colemans produce air that feels warm!  We've been using them at night for the past couple of weeks; we are very pleased.

Edited by docj
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There are heat pumps available that can heat at temperatures to - 15F.   Our minisplit was keeping us comfortable when the outside temp was 30F and was drawing about 550 watts.  Not all heat pumps are the same.  There are some very efficient models available and there are specifications that detail that efficiency for comparison.  It appears our minisplit is around 3 to for times more efficient than electrical resistance heating.

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25 minutes ago, GlennWest said:

We have seen 40's at night. Our mini splits have kept us comfortable. 

My Mini Split worked very well for me in Edmond, OK. last winter. Several days that didn't get out of the 20's and nights in the teens. My Coleman Mach would have been blowing very cold air, but the mini split has 80+degrees all the way to the front of my trailer with the unit at the opposite end. I have a wall unit in the bedroom, but it most of the time makes it too hot when it blows air so I keep it off while sleeping. The reversing during the coldest times is quite  a sound. I have never been outside near the ODU when it's happened, but it's very noisy. I recommend putting the ODU at the opposite end of where you sleep if possible. 

 

Rod

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