# How can I calculate usage of LP appliances?



## wdchuck (Jun 24, 2007)

Many of our appliances run on LP, I would like to figure out how much they each use, but lack the knowledge to do it. 

Doing the math for electricity is easy, LP is another matter. 

Thanks.


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## cfabe (Feb 27, 2005)

Just like electricity is measured in watts and watt-hours, heat is measured in btus and btu-hours. Each appliance should be rated in "input btu/h". So, for example, if you run a 50,000 btu/h heater for one hour, it will consume 50,000 btu of energy. Then you need to know that propane has about 92,000 BTU per gallon. So in that one hour usage of your heater you used 50,000/92,000=.54 or a little over a half gallon of fuel. 

For appliances like a water heater or furnace which cycle automatically you'll have to measure or estimate how much time the burner is on for. For something like a stove where you can vary the flame you'll just have to make a guess like 1 burner on high for 1 hour, etc.


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## wdchuck (Jun 24, 2007)

I looked at my stove, and the LP fittings read 78 (medium) burner, 56 small burner, and the large one has corrosion where the # would be. 

So 56 stands for 56,000 btus ?? 

With canning in the fall, and boiling lots of water, I'd like to figure in all my costs for preservation of foods. The other thing, is if I can do boiling on my horizontal barrel castiron woodstove, and ' cooking down ' certain foods, the fuel savings will add up. Knowing how much I can save, would be a real bonus.

Same thing with LP dryer versus line drying. It was a natural gas with LP orrifice installed, I'll have to see what the brass fitting reads.


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## Old Vet (Oct 15, 2006)

wdchuck said:


> I looked at my stove, and the LP fittings read 78 (medium) burner, 56 small burner, and the large one has corrosion where the # would be.
> 
> So 56 stands for 56,000 btus ??
> 
> ...


A cook stove and a Drier are really hard to calculate. You need to know if they are going to be used at full open or at a simmer how hot the sir is around them and a lot of other things. You can get an estimate from your LP gas dealer but it is only and estimate. What most of them will do is measure the orifice then tell you the most it can be. If that is what you need then go to any LP dealer and they will have a chart.


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## Windy in Kansas (Jun 16, 2002)

wdchuck said:


> I looked at my stove, and the LP fittings read 78 (medium) burner, 56 small burner, and the large one has corrosion where the # would be.
> 
> So 56 stands for 56,000 btus ??


No, that is the number for that specific orfice. Here is a link to a chart indicating BTUs. http://energy.growmark.com/propane/Chapter9.html


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## farminghandyman (Mar 4, 2005)

that number is most likely the "drill size" of the hole, some drills are numbered instead of fractional sizes,


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## wdchuck (Jun 24, 2007)

According to the chart, the larger the number, the fewer the btu's, which would be the opposite of the fitting usage. 
56 small burner....15,600 btu
78 medium burner.....1769 btu
100?? large burner....n/a

I'll try the LP dealer, see what he can offer.

Thanks anyway.


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## cfabe (Feb 27, 2005)

On the clothes dryer it has a thermostat too, so keep in mind that it's not going to be firing full blast the whole time it is running. On that it might be easier to hook it up to a grill tank temporarilly and run a load and weigh how much gas was used.


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