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Electricity vs propane


kb0zke

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For the first time we're in a place where we pay for electricity in addition to the camping fee. Does anyone know what the break-even point is for running the propane furnaces vs the electric heaters? The rate here is $0.10/Kwh. Don't remember what we paid for propane, but I think it was a bit over $2.00/gallon.

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Unfortunately, that chart doesn't take into account the fact that propane furnaces are notoriously inefficient.

 

BTU/unit Efficiency Effective $/unit $/btu 10,000 BTUS

BTU

Propane 91,333 70% 63933.1 $2.50 0.000039 $0.39

Electricity 3,412 100% 3412 $0.14 0.000040 $0.40

 

This Excel snippet shows that they are about equal when Propane is around $2.50/gallon and electricity is 14¢/KWH.

 

Easy calculation is take the KWH cost and multiple by 18.74 and that will give you equivalent cost/gallon propane.

 

Of course that doesn't count in how easy/uneasy getting refills for your propane tank may be. For those with removalable tanks, that isn't much of a problem - for a motorhome if you are in an area that won't allow mobile dispensing in RV Parks (like the city of Mesa, AZ), it mean unhooking, etc., or using an adapter to use an auxiliary tank with your motorhome.

 

For the winter in Arizona, we found that if we filled the tank for the winter, and used it for heat late at night on really cold nights, with space heaters during the day, we could go all winter without a problem on our 32 gallons (80% of a 40 gallon tank). Plus, in Mesa, electricity is cheap and propane isn't.

 

Barb

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Interesting and informative thread. Lowest price propane can often be found at Tractor Supply - currently about $1.99 / gallon in Cave Creek, AZ.

But propane entails some physical expenditures to get it. Plus, it mean "burning" and noise when the furnace is running.

When cost comparisons are as close as they are now, I prefer the quiet operation of an oil filled radiator for heat.

 

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On our fifth wheel, the furnace also heats the storage compartments and underside which may be important if the temp drops below freezing. Otherwise, for above freezing temperatures, the space heater only heats the interior space like zone heating. We even close off the upper bedroom most of the time, so one small space heater usually keeps the kitchen/living room comfortable even when it's 40's outside, (like Dallas this week).

Greg

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Propane vs Electricity facts


One kW hour of electricity is 3,412 Btu


One gallon of propane is 91,502 Btu


One pound of propane is 21,548 Btu



Conversion factors:


Multiply the propane price per gallon by 0.037 to give the equivalent price per kilowatt hour of electricity


Multiply the electricity price per kWh by 27.0 to give the equivalent price per gallon of propane


For those of us who pay by the pound/bottle:


The typical 20# tank holds 4.7 Gallons of propane


A 30# holds 7 Gallons of propane


Efficiency:


For heating applications most consider electricity as 100% efficient.


For each Kwh you get 3412 Btu exchanged to the surrounding medium, or the air in the RV with most electric heaters and to the water in

your water heater.


About 90% of that to the boiler of your refrigerator


Propane fired appliances of the typical RV variety have low efficiency.


The hot air furnace is the worst, with, about 65% efficiency.


Modern water heaters are a bit higher, probably close to 70% efficiency


The refrigerator is probably the highest, maybe 80-90% due to the enclosed space in the chimney.




In mixed usage, I would give the overall propane efficiency a 70%, and electricity is close to 100%.


This means, that a gallon of propane instead of 91,502 Btu only delivers a usable 64,051 Btu due to the losses in the appliances.


Or in other terms, the 20# bottle you just had filled only gives you 14# of usable Btu

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You can download a small program (app) that will do the simple calculation and also allows you to enter the appliance efficiency. According to an email to me from engineering at Suburban Manufacturing, the efficiency of RV furnaces ranges from 70 to 80 percent. Water heaters are 70 percent on gas.

You can download it HERE

 

Note: Because Microsoft in their infinite wisdom didn't include the software to support the older help file formats, for Windows Vista and higher you will need to download and install a Microsoft program that allows you to use help files with the "hlp" extension for whatever operating system you are using - if you want to use the help file (not really necessary to use the program)..
You can download it here Microsoft Knowledge Base. Scroll down to select your operating system. That doesn't work for Win10 however. Microsoft has not produced a patch for Win10.
The program is so simple that a help file isn't really needed. It just shows the info used to write the program and Kirk posted that above,
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Thanks, everyone. As I said, we're in a campground that charges $0.10/Kwh for electricity. We filled our 80-gallon (64 gallon usable) a few weeks ago, so we have plenty of propane for the time we'll be here. The two rooftop a/c units also have heat strips on them, and we have two propane-fired furnaces, one of which also heats the wet bay. What we've usually done is use the front rooftop heater as the main heat source, with the front furnace set to kick on at a slightly lower temperature. So far we've been able to stay in places that are warm enough that the rear heat hasn't been needed at all. I have a small electric heater set on the lowest setting in the wet bay, which helps keep things above freezing there. I wondered if we ought to turn off the roof heater and rely solely on the propane. It sounds like we're still in the range where the electricity is cheaper, so we'll keep on dling what we've been doing.

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Jimalberta, on 07 Dec 2016 - 3:02 PM, said:

Lol.....well I appreciate your posts. Lots of thought and common sense to them.

 

I also find your posts very informative and helpful. There will always be folks on forums that sometimes look but don't see what has been written, listen but don't necessarily hear and sometimes write/speak but basically say nothing. :)

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A AC with heat pump may be cheaper to operate BTU to BTU then a AC with heat strip. :)

 

Now a 80 gal LP tank on a MH is very unusual. Unless it was installed to run a LP engine.

My MH has a 40 gal for the LP generator and a 25 gal for the House. A total of 52 gal usable. Some D owners have tied the 2 tanks together.

 

Spec of a 1993 U300 say's it has 270 lb LPG tank which converts to 64.28 gal that would have 51.42 gal usable LPG. :) Which is still a very big tank.

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We do not stay in very cold climates we planned it that way . The coldest we can remember was 4 or 5 winters ago here in Florida near Disneyworld were it

got below freezing during the night and in the 40's and 50's for a day time high for nearly a whole month. We and everyone else were using a tank of propane every 3 days or so at 18.00 per refill. We used 10 tanks that month. We do not own a space heater and keep the heat set at 70 degrees.

 

Here at our Florida lot the electric is 13.258 per KH the bill for November was 750 KWH for 99.43 total bill we set the A/C at 78 and run the hot water and fridge on electric. We used 3 tanks of propane last winter (6 months) Propane her is 20.13 per fill.

 

We stay comfortable and use what we use.

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Really don't don't know why I bother posting

I appreciate your cost as expressed per 10,000 BTU.

Larger fuel cost are figured per million BTU or Mbtu.

I wish I could buy Diesel on a Mbtu basis when you pay per gal you don't know whether you get Good Diesel or Bio-Diesel there is a difference in BTU.

All fuels differ and BTU is a measure of energy.

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The tank says 80 gallons on it, which translates to 64 usable. One time I put 63 gallons into it (well, actually the guy from MFA put it in).

 

I like the idea of a heat pump. I think that when the time comes to replace an a/c unit I'll probably look at that possibility.

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Or just round everything off and use a 20:1 difference to determine which is cheaper, i.e. $2.00 per gallon propane costs about the same as 10 cents per KwH electricity to make heat by the time you figure in the exhaust waste, etc.

That's what I do, and it seems to work out fairly well. I initially found out about this ratio here on the Escapees discussion forum about 12 years ago, reviewed the calculations to confirm the ratio, and used it ever since.

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Or just round everything off and use a 20:1 difference to determine which is cheaper, i.e. $2.00 per gallon propane costs about the same as 10 cents per KwH electricity to make heat by the time you figure in the exhaust waste, etc.

Actually, that same rule can be applied to a stick house as well. At our home-base we have both electric and propane heat and this gets you close enough for most purposes, since I don't think that any of us can probably get much closer than that. I have used the formula that I posted above, and which I got from Mark Nemeth, but it typically comes out pretty close the the much easier, 20:1 method. It's pretty easy to check what you pay per KwH and multiply by 20 and compare to propane costs, although it can be fun to work the numbers if you happen to be bored. Barb's figures make it more like 18:1.

 

All of that is based upon the typical resistance heaters, but what are the efficiency for a heat pump system? Energy.gov says that a heat pump can supply 1.5 to 3 times the heat energy compared to the energy used to operate it. But you also get into outside temperatures. In our case, we have a heat pump in our home-base and that system seems to operate pretty well down to about 40 degrees but it becomes an electric resistance heater as temperature falls and that costs more and isn't 100% efficient since the blower and duct work come into play.

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Since we sometime park fairly long term in a park where Propane IS NOT AVAILABLE TO THE MOTORHOME I have studied this topic and debated to use LP or electric, but for me convenience is an important factor as heating (regardless of method) isn't all that expensive. However, the inefficiency of typical forced air LP furnaces is bothersome to me versus electric's 100%. I have studied a few what may be called "forced air ventless heaters" that have a small 12 VDC circulating fan that draws in combustion air from the outside and of course the traditional ventless where you must leave a window open. I have also studied fabricating an outside dryer type vent (you can open and close) to furnish fresh combustion air to the stove bottom plus leave a window cracked near it and use not one but two CO detectors and use it ONLY in daylight hours. No need to flame on me or quote articles regarding safety, I have read those and am aware of safety issues and ONLY said I have "studied" alternatives. Also the modern electronic controlled so called High Efficiency LP Furnaces (and also heat pumps) are something I've given though to but not yet researched as Ive ONLY seen them in homes so far. In the short term I plan to do nothing and continue use of the forced air LP furnace despite its inefficiency grrrrrrrrrrrr lol but the engineer in me makes this an interesting topic.

 

John T

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I suspect the only reason we aren't seeing 95% efficient LP furnaces in RV's is money. We, the consumer must be willing to pay for the efficiency.

 

After reading this thread, I went down in my basement and really looked at how our house furnace (98%) is built. The actual LP burners and heat exchanger are about the same size as my entire MH LP furnace, the rest of the cabinet is electronics and a condensate collector + air filter, about 2/3 is empty space. The air filter is the same size as the one in my MH's basement air conditoner so that's a wash.

Any design engineers want a project? With a patent you could be the next millionaire, selling to Foretravel, Prevost, etc.

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After reading this thread, I went down in my basement and really looked at how our house furnace (98%) is built. The actual LP burners and heat exchanger are about the same size as my entire MH LP furnace, the rest of the cabinet is electronics and a condensate collector + air filter, about 2/3 is empty space. The air filter is the same size as the one in my MH's basement air conditoner so that's a wash.

Mind sharing what your furnace make/model happens to be? We heat our home-base with propane when too cold for the heat-pump.

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