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Old 02-22-2010, 03:53 AM   #1
Lou1998
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Default Electric vs. Propane Brewing

After reading some of the threads on using electric heating elements to brew, I was curious how electric brewing compares to using a propane burner, both in terms of time and money. So, I did some thermodynamics homework and this is what I discovered. Feel free to point out any flaws you see. This wasn’t my best subject although its nice to finally find a use for it.

First, here are a few definitions to establish a common framework for this discussion.

It takes 1 BTU/hr to raise 1 lb of water 1 deg F.

1 gallon of water weighs 8.3 gallons, so it takes 8.3 BTU/hr to raise 1 gallon 1 deg F.

1kW = 3414 BTU/hr

So, to raise 5 gallons of water from 60 F to boiling would require 5*152*8.3=6308 BTU/hr.

This analysis does not take into account any thermal loss (cooling) because the loss would vary based on outside temperature, material of the vessel, surface area of the opening, etc. Regardless if you use electricity or propane, insulating your hot liquor tank and brew kettle will help you achieve your target temperature more quickly and maintain that temperature with less energy.

Propane burners are rated on BTU/hour or simple BTUs. They range from 35k-200k BTU/hr. This is the amount of energy produced by burning the propane, but not necessarily transferred to heat the water. So, it is not a perfectly efficient transfer to your HLT or boiling kettle. There will be further loss from the vessel itself since it is not a perfect conductor. It is difficult to determine the actual amount of energy produced by the burning propane that actually makes its way into heating the water. Therefore, I will make an assumption that only 50% of the energy produced by a propane burner actually heats the water. A quick google search turned up the King Kooker turkey fryer produces 54K BTUs/hr. Adjusting for efficiency, the propane burner provides 27,000 BTU/hr (54,000*.70). Based on this value, the propane burner could bring 5 gallons of 60 F water to boil in 14 minutes (6308/27,000*60min). Obviously, a more powerful burner will heat water more quickly, but with greater fuel consumption.

Electric heating elements are usually measured in watts or kilowatts (kW). A 4kW heating element would provide 13,656 BTU/hr (remember, 1kW = 3141 BTU/hr). The electric heating element would be much more efficient at transferring its energy into heating the water because it is submerged in the water and has negligible loss. Therefore, the 4kW electric element could bring 5 gallons of 60 F water to boil in 27.7 minutes (6308/13,656*60min).

However, which heat source is more cost effective?
Propane contains 21,622 BTUs per pound. (http://www.propanegas.ca/FileArea/PG...properties.pdf )

Therefore, a 20 lb tank of propane would have 432,440 BTUs of energy. That is enough to run your 54K BTU propane burner for approximately 8 hours. Assuming $20 per tank, propane use costs $2.50/hr.

According to my last electric bill, I paid $.18 per kilowatt hour after taxes and fees. Using a 4kW electric heating element for one hour would use 4 kW hours of electricity and cost $.72/hr.

Electricity is certainly less expensive to operate but more costly in terms of time. Using my example above, electric brewing would increase the time to reach strike temperature for your mash by 10 minutes (21 min for electric vs. 10.6 min for propane). It would take an additional 6 minutes to reach boil after the sparge (12 min for electric vs. 6.06 min for propane). Sparge water can be heated during the mash so there is no time savings associated with propane. Overall, for a 5 gallon batch, you can expect to save about 16-20 minutes using propane over electric.

The only drawback to electric brewing I can think of is ready-made equipment is difficult to acquire. Propane turkey fryers with 28-32 quart pots are commonplace and relatively easy to operate. From what I have seen on the forums, most electric brewers use home-made equipment that can be dangerous if you don’t know what you are doing. If you chose to explore brewing using electricity, take appropriate safety precautions and understand the associated risks.

In conclusion, electric brewing offers an affordable alternative to propane. Although it may add a few minutes to your brew session, it offers the flexibility to brew indoors and in confined spaces where propane use would be unwise and likely dangerous. Finally, you don’t have to worry about running out of propane, as I am sure we have all done or will do during a brewing session.

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Old 02-22-2010, 03:58 AM   #2
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Some common misconceptions in your calcs. But you did your work! I like it!

Here is a recent post that I put up to discuss some of the misconceptions about electric brewing.


Misconception:
ELECTRIC????? I don't get it. Out west it cost more and is less efficient. Gas is cheep and with 170,000 BTU gas burners you can't beat it. I have never heard of inexpensive electric burners that will put out that much. Electric? No way!!


Not true at all.

Gas burners are about 25% eff at getting BTUs to the kettle. Electricity is basically 100% efficient. A 170,000 BTU burner will produce the heating power of 43,000 BTUs, that is the extent of it. If a 170,000 BTU burner provided 170,000 BTUs of heat to your kettle, youd get 13 gallons from 60F to a boil in 6 minutes flat, and it doesnt.

Electricity in California is not that expensive. In Antioch you pay $.14 per kWh, here in Indiana I pay $.10 per kWh. That is quite average across this great land.

A 20lb tank of propane contains about 17 pounds of propane, or 374,000 BTUs. If you are going to net 25% of that, you are getting about 95,000 BTUs from that tank at a cost of about $16.

1kW is 3412 BTUs... so you need about 28,000W or 28 kW to equal the same 95,000 BTUs in a 20lb tank of propane. In Indiana that would cost me $2.80, in California that would cost you $3.92. If you pay $.57 per kWh, then it would be equal to the cost of propane anyhow.

Speed of heating. This is tied to BTU output, and since electricity is so much more eff. at getting the BTUs into the kettle to do work, you need a lot fewer total BTUs to get the same outcome.

A 9000W kettle like I have will heat 13 gallons from 60F to boiling in 34 minutes. That is 30,708 BTUs, the equivelant of a 123,000 BTU burner, at 1/5 the cost to operate.

Bottom line, electricity is fast, cheap and clean.

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Old 02-22-2010, 04:36 AM   #3
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Ummm.... I just read this thread, and now I need a beer. Good information however.

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Old 02-22-2010, 04:38 AM   #4
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The Pol, Jkarp, and Boerderij_Kabouter, are my heroes! I have decided to go all eclectric in my brewing adventure, it will take me a couple of years to get all of my e-equipment together, but you sirs are the three wise men of eBrewing!!! All the research is concrete when it comes to cost/efficiency ratios. Pol...Kill-A-Watt is beautiful, I have been following your thread, and all I can say is I envy your system, and I revel in its beauty and simplicity (minus the electronics, of course)

Anyhow, you guys keep up the great work, and continue to teach us that electricity (at least for brewing) can be our greatest ally.

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Old 02-22-2010, 04:40 AM   #5
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Quote:
Originally Posted by Schnitzengiggle View Post
The Pol, Jkarp, and Boerderij_Kabouter, are my heroes! I have decided to go all eclectric in my brewing adventure, it will take me a couple of years to get all of my e-equipment together, but you sirs are the three wise men of eBrewing!!! All the research is concrete when it comes to cost/efficiency ratios. Pol...Kill-A-Watt is beautiful, I have been following your thread, and all I can say is I envy your system, and I revel in its beauty and simplicity (minus the electronics, of course)

Anyhow, you guys keep up the great work, and continue to teach us that electricity (at least for brewing) can be our greatest ally.
Thanks, that is flattering.
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Old 02-22-2010, 04:50 AM   #6
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Quote:
Originally Posted by Schnitzengiggle View Post
The Pol, Jkarp, and Boerderij_Kabouter, are my heroes! I have decided to go all eclectric in my brewing adventure, it will take me a couple of years to get all of my e-equipment together, but you sirs are the three wise men of eBrewing!!! All the research is concrete when it comes to cost/efficiency ratios. Pol...Kill-A-Watt is beautiful, I have been following your thread, and all I can say is I envy your system, and I revel in its beauty and simplicity (minus the electronics, of course)

Anyhow, you guys keep up the great work, and continue to teach us that electricity (at least for brewing) can be our greatest ally.
Quote:
Originally Posted by The Pol View Post
Thanks, that is flattering.
I'm not as savvy as all of you engineering folks round here, so as long as I can count on your advice when time comes, the very least I can do is give some credit where credit is due!
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Old 02-22-2010, 04:52 AM   #7
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Quote:
Originally Posted by Schnitzengiggle View Post
I'm not as savvy as all of you engineering folks round here, so as long as I can count on your advice when time comes, the very least I can do is give some credit where credit is due!
Kill-A-Watt is beautiful, more beautiful than I had planned... this forum has taught me well
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Old 11-28-2010, 05:21 PM   #8
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Quote:
A 9000W kettle like I have will heat 13 gallons from 60F to boiling in 34 minutes. That is 30,708 BTUs, the equivelant of a 123,000 BTU burner, at 1/5 the cost to operate.
Reviving a dead thread...
How did you get 30,708 BTUs needed for heating 13 gallons of wort?

What I came up with is
13 gallons of water * 8.345 lbs/gal = 108.5 lbs

212-60=152 degF temp rise

108.5 * 152 = 16492 BTUs

I realize wort is heavier than water, but not that much, or am I missing something?

I'm tired of blasting through BBQ propane tanks at $15/tank, and am thinking about building an electric rig, which is cheaper even with Connecticut rates at $.25/KW! I might look into improving the propane burner efficiency first, though. Thinking about adding fins to the bottom like camping stoves.
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Old 11-28-2010, 05:46 PM   #9
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It may take 16492 BTUs to raise the water from 60-212 given zero heat loss, which is impossible. Then, it takes extra BTUs to take it from 212 to boiling. I know it's 970 BTUs to turn a pound of water into steam.

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Old 11-28-2010, 06:02 PM   #10
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I brew with propane (using the familiar 20 lb. cylinder) and have the potential of running a line from our 1,000 gal. bulk tank, which would cut my costs more than in half. However, there is absolutely no question that for efficiency, electric is the way to go. Providing a 240VAC / 30A circuit is no problem, & I've seen several pretty likely designs, but am looking for a boil pot that does a good job of accommodating an immersion chiller (and, no, I have no interest in plate, counterflow, or other "internal" chiller).

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