Check my calcs! How quick will electricity pay for itself?

[DKershner]

I agree with your calculations. But you are not accounting for efficiency. Electric will be nearly 100% delivered effeciency and propane will be no where near that. This seem obvious when I boil in my garage with propane and it gets hot in there even with the door open. And you do not want to stand too close to the burner. A lot of BTU's are not making it into the wort. For sake of argument if you apply 25% to propane, It makes electric cheaper by half.

Yeah, this is where the direct comparison to the two fuels differ, unless someone can find a way to burn propane and get the heat directly to the wort. I think it would be steam-related...

Also, around here there's only hydroelectric, no coal. Electricity screws up rivers, not air around here, not that I would want to necessarily use either.

 

[Torg]

So how do you calculate how many KWh it takes to make a batch of beer? It seems to me that with a 5500w element boiling for an hour I would only be using 5.5KWh. That would be considerably less then what it would cost to boil a batch of beer with propane.

Edit: also you only need 10 gauge wire for a 30a circuit.

It depends on the temperature you start with. But for the sake of argument let us assume it is at 70F.

BTU is 1lb of water, 1 degree F, for one hour. So to get 6 gallons of water (it is not exactly the same for wort, but you will get an idea) you need 7071.6 BTUs, or 49.8 lbs x (212F - 70F). This would take .07 gallons of propane or about 19 cents worth at $2.50 a gallon. However this assumes 100% efficiency of the burner. Many are only about 75% efficient, so it will take about 9500 BTUs to achieve this or about 25 cents of propane.

1 watt = 1 Joule/sec, so one hours worth would be 3600 watts. One 1KWh would be 3600000J. You will need 7,627,200J to bring 6 gallons of water to a boil. It would take approximately 2.1KWH then to achieve the same thing or about 63 cents worth of electricity. An electric immersion element is very efficient as it is in direct contact with the liquid. This assumes 100% but it is really more like 90% (depends on element). so adjusting for efficiency we get 70 cents of electricity (and I did not include the SSR loss, controller or other elements, since we are strictly talking about fuel).

Of course adjust these according to your fuel costs. But in a general sense the most expensive way to create heat is with electricity.

And you are correct it takes 10 gauge not 8, I looked up the wrong value on the chart. But you will need to rewire a special receptacle and circuit breaker for it.

 

[lschiavo]

Many are only about 75% efficient

I have a hard time believing 75%. I heat my strike and sparge water in my electric HLT (uninsulated) and it does not heat up my garage like when I fire up the propane for a boil. I am not saying you are wrong, I have never tried to calculate this myself so have no idea. What is your source for this?

 

[DKershner]

I guess I took 25-40% efficiency as fact. I can test how much energy it takes to heat up some water during my next brew day by weighing before and after.

Actually, I will probably have to do it separately. 1 propane tank and 3 burners with a HERMS has to be hard to calculate.

 

[lschiavo]

I guess I took 25-40% efficiency as fact. I can test how much energy it takes to heat up some water during my next brew day by weighing before and after.

Actually, I will probably have to do it separately. 1 propane tank and 3 burners with a HERMS has to be hard to calculate.

I would be curious to know your results. Cause I'm a big geek

 

[DKershner]

I would be curious to know your results. Cause I'm a big geek

Well, I just got a new system, it needs testing! I will try and make time to boil up 10gallons tonight.

How do I account for the heat escaping through the walls of the pots? If electric is seen as 100% efficiency, the escaping through the walls must not be in the efficiency calc.

 

[Torg]

I have a hard time believing 75%. I heat my strike and sparge water in my electric HLT (uninsulated) and it does not heat up my garage like when I fire up the propane for a boil. I am not saying you are wrong, I have never tried to calculate this myself so have no idea. What is your source for this?

It was based upon competitive sites as the efficiency of their burners (as opposed to say a Bayou Classic). And a bit off my own observations. It takes about 15 minutes or so to bring 5 gallons of water at 65F (the temp of my well water) to 212F. To do so would require about 10,000 BTUs and off my burner at 55,000 BTU that is about correct for a 75% rate. I have never timed it directly, but you can take your own observations or the marketing data as a source.

Keep in mind the loss of efficiency is from the escaping heat. It takes about 0.02 BTUs to raise a cubic foot of air 1 degree F. So If your propane burner is letting 3000 BTUs go out you can see why it heats up the garage so fast. And electric heater has a much higher efficiency, meaning all its extra heat goes into the liquid.

 

[lschiavo]

Well, I just got a new system, it needs testing! I will try and make time to boil up 10gallons tonight.

How do I account for the heat escaping through the walls of the pots? If electric is seen as 100% efficiency, the escaping through the walls must not be in the efficiency calc.

I would think heat loss by the vessel would be similar regardless of the fuel and would be very difficult to calculate anyway.

 

[DKershner]

I would think heat loss by the vessel would be similar regardless of the fuel and would be very difficult to calculate anyway.

I agree with you, but I cannot easily convert my pots to electric and compare directly.

I can calculate how long it takes me to heat water and how many lbs of propane I use, but the comparison to electric would not be a fair one unless the efficiency number also had vessel loss in it, which 100% obviously does not.

 

[lschiavo]

It was based upon competitive sites as the efficiency of their burners (as opposed to say a Bayou Classic). And a bit off my own observations. It takes about 15 minutes or so to bring 5 gallons of water at 65F (the temp of my well water) to 212F. To do so would require about 10,000 BTUs and off my burner at 55,000 BTU that is about correct for a 75% rate. I have never timed it directly, but you can take your own observations or the marketing data as a source.

Keep in mind the loss of efficiency is from the escaping heat. It takes about 0.02 BTUs to raise a cubic foot of air 1 degree F. So If your propane burner is letting 3000 BTUs go out you can see why it heats up the garage so fast. And electric heater has a much higher efficiency, meaning all its extra heat goes into the liquid.

Honestly, I have never looked up specs for propane burners. We had one when we started brewing and just went with it. I tend to trust your observations much more than manufacturer claims. Have you ever checked your actual fuel useage (gallons or pounds) against your time calcuation?

I never knew that figure for raising air temp. A little goes a long way there.

 

[lschiavo]

I agree with you, but I cannot easily convert my pots to electric and compare directly.

I can calculate how long it takes me to heat water and how many lbs of propane I use, but the comparison to electric would not be a fair one unless the efficiency number also had vessel loss in it, which 100% obviously does not.

I see your point. That throws another wrench into it. What are you boiling in? Stainless compared to other metals is relatively non-conductive...Another reason direct fired vessels may be less effecient.

I have heated water in my uninsulated (covered) HLT to 125, left it at about 50 degree ambient temps for over 12 hours and come back to 85 degree water. So, if we are talking similar vessels, the heat loss from the vessel itself should be negligible at least for our purposes.

Also, we agree that electric cannot be assumed at 100% There are losses between the meter and element. If we figure electric at 95% we can at least get some comparison.

 

[Torg]

Honestly, I have never looked up specs for propane burners. We had one when we started brewing and just went with it. I tend to trust your observations much more than manufacturer claims. Have you ever checked your actual fuel useage (gallons or pounds) against your time calcuation?

I never knew that figure for raising air temp. A little goes a long way there.

I never looked them up either until this thread came up. Price per pint is not exactly why I brew beer. And I calculate the cost of each batch more on the ingredients then anything else. The burner I purchased as a Turkey Fryer at a local HEB. I live in Texas and a Turkey Fryer is about as common as dirt.

And since I fill my own tank off my 250 gallon tank I am pretty sure that I use more then 20# to fill a 20# tank. My numbers were not really to be exact but more about how I view the cost of propane vs electricity. I tend to think of it as electricity is twice as expensive.

Then again I spend allot of my time out at our ranch which is off grid. Meaning if I wanted to put in a 30A 120V circuit I would have to have a pretty hefty bank of batteries, an inverter and some way to recharge it (solar/wind). It is about 20 miles from the closest electrical pole and I am not paying to get the poles installed. I find propane much easier to use and sort of enjoy brewing outdoors anyway. But if you lived in an apartment I can fully appreciate the need to use electricity over gas.

 

[DKershner]

I am using 18 or 20ga SS pots.

I agree with you that at 125deg the effect is probably fairly minimal, but that would grow as you get higher and higher in temp.

I can measure from as cold as possible (probably around 60) to about 125 to minimize this effect. I will also have it covered. Ambient temp tonight should be higher than normal, around 50, so it's a good day to try.

 

[lschiavo]

I never looked them up either until this thread came up. Price per pint is not exactly why I brew beer. And I calculate the cost of each batch more on the ingredients then anything else. The burner I purchased as a Turkey Fryer at a local HEB. I live in Texas and a Turkey Fryer is about as common as dirt.

And since I fill my own tank off my 250 gallon tank I am pretty sure that I use more then 20# to fill a 20# tank. My numbers were not really to be exact but more about how I view the cost of propane vs electricity. I tend to think of it as electricity is twice as expensive.

Then again I spend allot of my time out at our ranch which is off grid. Meaning if I wanted to put in a 30A 120V circuit I would have to have a pretty hefty bank of batteries, an inverter and some way to recharge it (solar/wind). It is about 20 miles from the closest electrical pole and I am not paying to get the poles installed. I find propane much easier to use and sort of enjoy brewing outdoors anyway. But if you lived in an apartment I can fully appreciate the need to use electricity over gas.

I believe electric would be much more expensive for you in your situation. I dont see you converting. Hank Hill would be proud

 

[DKershner]

I never looked them up either until this thread came up. Price per pint is not exactly why I brew beer. And I calculate the cost of each batch more on the ingredients then anything else. The burner I purchased as a Turkey Fryer at a local HEB. I live in Texas and a Turkey Fryer is about as common as dirt.

And since I fill my own tank off my 250 gallon tank I am pretty sure that I use more then 20# to fill a 20# tank. My numbers were not really to be exact but more about how I view the cost of propane vs electricity. I tend to think of it as electricity is twice as expensive.

Then again I spend allot of my time out at our ranch which is off grid. Meaning if I wanted to put in a 30A 120V circuit I would have to have a pretty hefty bank of batteries, an inverter and some way to recharge it (solar/wind). It is about 20 miles from the closest electrical pole and I am not paying to get the poles installed. I find propane much easier to use and sort of enjoy brewing outdoors anyway. But if you lived in an apartment I can fully appreciate the need to use electricity over gas.

Solar powered brewing would put us all to shame.

 

[lschiavo]

I am using 18 or 20ga SS pots.

I agree with you that at 125deg the effect is probably fairly minimal, but that would grow as you get higher and higher in temp.

I can measure from as cold as possible (probably around 60) to about 125 to minimize this effect. I will also have it covered. Ambient temp tonight should be higher than normal, around 50, so it's a good day to try.

Well, post up the results. Just thinking and wondering what the difference would be for a sustained a boil for an hour. I think the conductivity of the kettle would really come into play here.

 

[DKershner]

Well, post up the results. Just thinking and wondering what the difference would be for a sustained a boil for an hour. I think the conductivity of the kettle would really come into play here.

It would on both accounts, the heat getting in through the bottom and the cold getting in through the sides and top. My personal opinion is that this would muddy the results, since it depends more on the pot, ambient air temp, wind speed, etc than the actual burner.

 

[lschiavo]

It would on both accounts, the heat getting in through the bottom and the cold getting in through the sides and top. My personal opinion is that this would muddy the results, since it depends more on the pot, ambient air temp, wind speed, etc than the actual burner.

I think electric would really shine with a sustained boil. The heat with electric is applied directly to the liquid inside the vessel and only has resistance getting out. A direct flame has to get past the resistance of the vessel to get the heat to the liquid in the first place. The more thinking I do on it, I believe this is what will make the most difference.

But, yes this would muddy things. Lets see what it would take to get to a boil first

 

[DKershner]

I think electric would really shine with a sustained boil. The heat with electric is applied directly to the liquid inside the vessel and only has resistance getting out. A direct flame has to get past the resistance of the vessel to get the heat to the liquid in the first place. The more thinking I do on it, I believe this is what will make the most difference.

But, yes this would muddy things. Lets see what it would take to get to a boil first

I feel like sustaining the boil hardly takes much energy at all. Sure, it is on for a long while and is probably a good portion of the energy use, but I barely even have the burner on during that phase, and you electric guys turn your PID's down pretty far too.

I feel the opposite (though neither of us really knows), that the way up and the boil itself will be exactly the same efficiency for both. This is, unless one vessel is more well insulated than the other, in which case it would shine at the boil levels, but that's not really a fair comparison anyway.

You could make the argument that an electric vessel is easier to insulate though, THEN electric would shine at a sustained boil.

 

[Torg]

It would on both accounts, the heat getting in through the bottom and the cold getting in through the sides and top. My personal opinion is that this would muddy the results, since it depends more on the pot, ambient air temp, wind speed, etc than the actual burner.

Well as long as we are getting picky you would have to know the recipe and the SG as well. The higher the gravity the more it will take to heat it. Loss due to surface cooling would probably be much higher (evaporation vs convection). So maybe use a lid to negate pot dimensions.

Also you may want to take into effect the fact that electricity, at least in the US, is quite dirty. That is to say it is seldom exactly 120V@60Hz. Anyone with a power correcting UPS can tell you about that. And I do not know how much that would effect the efficiency of an electric element.

Hank Hill is not exactly my hero but if I did not hear that burner while I was brewing something would not feel right. I think I am pretty much at peace with "it is somewhere about 2x the cost" then anything else. Although I would be interested in the results.

 

[DKershner]

Well as long as we are getting picky you would have to know the recipe and the SG as well. The higher the gravity the more it will take to heat it. Loss due to surface cooling would probably be much higher (evaporation vs convection). So maybe use a lid to negate pot dimensions.

SG of 1.000, since we are using water to test.

Our results are going to be anything but exact, but that wasn't exactly the point of this post either.

 

[Torg]

I think electric would really shine with a sustained boil. The heat with electric is applied directly to the liquid inside the vessel and only has resistance getting out. A direct flame has to get past the resistance of the vessel to get the heat to the liquid in the first place. The more thinking I do on it, I believe this is what will make the most difference.

But, yes this would muddy things. Lets see what it would take to get to a boil first

Actually the numbers I looked up assume it is over and hour use. Joules are in KWh and a BTU is 1 degree over and hour. So they both have an hour boil built into the calculation. Still I would like to see someone else numbers.

 

[DKershner]

Actually the numbers I looked up assume it is over and hour use. Joules are in KWh and a BTU is 1 degree over and hour. So they both have an hour boil built into the calculation. Still I would like to see someone else numbers.

I would also need to calculate exact boil off in that case as well...plus I am at 4000ft+ elevation...that must have some effect on boil.

I think for now I will stick to straight "How much and how long does it take to heat 10gal of water from 60F to 125F with my burner?" We can get complicated from there, I need to leak test my mash tun tonight anyway.

 

[Brewmoor]

Solar powered brewing would put us all to shame.

I am hoping to do just that. Right now the federal government is giving huge tax rebates for solar and wind. I have a ton of both here in colorado. They are also giving even larger incentives to businesses that convert to systems that connect to the grid. We are in the process of starting a taproom. We will eventually offset our power use. (electric brewery) with solar and or wind.

Right now though. I am spending much less per brew using electric then i was with propane. I could do about 3 brews from a blue rhino exchange. The cost of that was about $23 (everything is more expensive in Vail). So lets say $7 per 10 gallon batch. Well with a 5500 watt element and a PWM circuit to control how often the element "fires" I am spending about $3 per brew during peak hours. I am not sure why this thread is getting so complicated with efficiency and material types of kettles. It is a pretty easy breakdown. Electric is much cheaper if you are not buying your propane is bulk.

 

[DKershner]

I am hoping to do just that. Right now the federal government is giving huge tax rebates for solar and wind. I have a ton of both here in colorado. They are also giving even larger incentives to businesses that convert to systems that connect to the grid. We are in the process of starting a taproom. We will eventually offset our power use. (electric brewery) with solar and or wind.

Right now though. I am spending much less per brew using electric then i was with propane. I could do about 3 brews from a blue rhino exchange. The cost of that was about $23 (everything is more expensive in Vail). So lets say $7 per 10 gallon batch. Well with a 5500 watt element and a PWM circuit to control how often the element "fires" I am spending about $3 per brew during peak hours. I am not sure why this thread is getting so complicated with efficiency and material types of kettles. It is a pretty easy breakdown. Electric is much cheaper if you are not buying your propane is bulk.

Solar gets crazy credits here too, around $3/watt from Oregon alone, but even if I covered my entire south facing roof with panels, I couldn't even cover my household's normal electric usage, much less brewing. I will probably do so later in the year, but it is mostly irrelevant to the current conversation.

So, in your case you save $4 a batch, which is cool. Not sure how much just one element and a PWM cost you, but since you aren't doing any automation, it was probably a bit cheaper than what I am talking about. Either way, even with your insane costs, it would take me about 275 brews to break even on electric.

The reason the thread is getting complicated is because we answered my question, and Torq's too, but we are trying to find out now a real comparison between electric and propane, not just locales.

 

[Brewmoor]

If you can connect your panels to the grid you will be suprised how much you will get out of it. You will be sending power to the grid when you are not using it. I bet a 6Kw system would (which is what the government cutoff for rebates caps at) would have you paying very little in electricity bills per year.



My system cost about $1500 so yeah it would take about 375 brews to pay that with the difference in what I am saving. This is my first rig though. So my only loss was the price of the turkey fryer i was using. In my case I was looking at what I would save between building my first system to use propane or electric. I was starting from scratch.

 

[DKershner]

If you can connect your panels to the grid you will be suprised how much you will get out of it. You will be sending power to the grid when you are not using it. I bet a 6Kw system would (which is what the government cutoff for rebates caps at) would have you paying very little in electricity bills per year.

6Kw would more than cover my household and brewing.. I live in one of those uber-efficient houses though so the roof is small. I could maybe fit 3Kw up there. Oregon's residential cutoff is at 2Kw anyway for their tax credit.

My system cost about $1500 so yeah it would take about 375 brews to pay that with the difference in what I am saving. This is my first rig though. So my only loss was the price of the turkey fryer i was using. In my case I was looking at what I would save between building my first system to use propane or electric. I was starting from scratch.

Starting from scratch makes a bit of a difference, cause you can subtract the cost of what a propane system would cost, and 375 brews is probably doable either way, though on the upper end of the scale of what I would call feasible. Mine was more like 500-700 though.

 

[DKershner]

Realized my scale wasn't very accurate, but oh well.

.5lbs of propane used.
Starting temp 67F
Ambient Temp: 65F
8gal of water

4:00 - 80F
7:00 - 93F
10:00 - 104F
13:00 - 116F
15:47 - 125F

 

[DKershner]

3712 BTU needed (8lbs/gal * 8 gal * 58deg)
11000 BTU used (about)

34% efficiency.

 

[DKershner]

11000 BTU over 15:47 = 41905 BTU burner. Wasnt quite at full blast.