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

OK, this is going to get a little complicated, but I just need to know if everything I am writing makes sense. I am considering a switch to electric and am just trying to see how long it would take to pay for itself in # of batches. Bear with me here.

OK, so I currently use high pressure propane in 20lb tanks. I buy the propane at a gas station which charges $2.19/gal. 20lb propane tanks would hold a 4.71gal of propane. This means the propane tank costs about $10.31 to fill. How much propane I use depends on season, weather, etc, but on average I use about 1/3 of the tank for a 10gal brew session, or about $3.43. I also use my hot water heater to heat the water if this number seems low, but that would be the case for either system.

Since the tank has about 400,000 BTUs in it, that means I use about 133,333 BTU/session. At 25% efficiency, which I think is common for burners, that means I get 33333.25 BTUs to the wort. To achieve that many BTU's with electric, I would need 9.7kW (3412BTU/kW). I pay about $.13/kW around here, or $1.26/session.

$3.43 (propane) - 1.26 (electric) = $2.17 savings/session.

I figure to wire a 240V outlet and get a system from brewmation to handle the HLT and BK would be around $1000, with some misc costs that we will call $100.

$1100 / $2.17 = 506 brew sessions.

Does anyone see an error here? Do my calculations seem biased somewhere? I realize the benefits of automation are not accounted for, but anything else?

Thanks for any help you can give,
DK

What it looks like is you are trying to calculate the ROI on purchasing equipment. You found your savings number with $1.40 per session. That is your compared savings in relation to your process.

785 brews would be your ROI for the equipment if you are calculating this only with your process savings. You have to also consider other Variables. Life cycle of old system and it's replacement cost. Maybe too the time savings with electric. You might save even more money if you can build the system yourself and do the wiring yourself.

785 brews is not a realistic number for ROI. If you are strictly sticking to that number. Then it would not make sense to upgrade. You will never see a savings.

Right, apologies on this, I should've been a little more clear. This is just a comparison for ME. There are much more cost effective ways to go electric and knowledge can save you quite a bit. I do not have this knowledge and would kill myself making an electric system.

I also do realize that 785 brews is a number that is basically the same thing as saying 'not worth it'.

Your life cycle point in an interesting one, however the replacement cost on turkey burners is pretty low, and would last fairly long. Anything else in my system would be reused on the electric system.

Time savings is an interesting point. It would probably heat a little faster and would require much less attention. I may assign a value to that.

I think this would be similar but looking at it from a different perspective:

To heat 10 gallons from 60 to boiling:

[212-60]x10gal(8.35lb/gal)=12692 BTU / 3412 BTU/kWH = 3.7kWH @ .13 = $0.481

propane has 21584 BTU/lb: 12692BTU/lb / 21,548 = .59lbs @ $0.90/lb = $0.531 (insert your propane cost)

if propane is 25% efficient propane heating cost would be x4 = $2.124

So, 2.124-0.481= $1.64 savings to boil 10 gallons.

Propane theoretically looks to be about 4.5 times more costly assuming 25% for propane.

$.9/lb for propane seems costly. Is this the price to exchange Blue Rhino tanks? According to my calcs, I am paying about half of that. If I pay $2.10/gal of propane, and 4gal is about 18lbs, that means about $8.4/tank, or $.46/lb.

Are any of those assumptions wrong?

I agree that your model looks to be doing the same thing as mine, but mine is about showing about a 2.25x cost for propane, not 4.5x.

dkershner said:

$.9/lb for propane seems costly. Is this the price to exchange Blue Rhino tanks? According to my calcs, I am paying about half of that. If I pay $2.10/gal of propane, and 4gal is about 18lbs, that means about $8.4/tank, or $.46/lb.

Are any of those assumptions wrong?

I agree that your model looks to be doing the same thing as mine, but mine is about showing about a 2.25x cost for propane, not 4.5x.

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I am sure you know what your cost is. Are you talking a 20-lb tank. In my experience only bulk fills are calculated by the gallon. I am not sure of the exchange costs. I have an electric HLT and I boil with propane and use a 100lb tank. Last fill It cost $76. That is .76/lb. I assumed smaller quantities may be more expensive. Just plug in your cost per pound and see where that puts you.

I have never calculated how much propane I use per brew. I am not sure how accurate 25% efficency for propane is either. I am sure it would vary with conditions. The caculations I showed assume 100% efficiency which will be close with electric. Just apply what you feel as a reasonable efficency for propane.

lschiavo said:

I am sure you know what your cost is. Are you talking a 20-lb tank. In my experience only bulk fills are calculated by the gallon. I am not sure of the exchange costs. I have an electric HLT and I boil with propane and use a 100lb tank. Last fill It cost $76. That is .76/lb. I assumed smaller quantities may be more expensive. Just plug in your cost per pound and see where that puts you.

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If your 100lb tank costs .76/lb, I must be off on my calculation. I am using 20lb tanks and fill them at a gas station. It isn't a swap, it's a fill, just like you would a car. The current cost is around $2.10/gal at the ones near my house.

I pulled the figure of 4gals per tank from here: http://answers.yahoo.com/question/index?qid=20070616040854AAdKgt4
OR
http://wiki.answers.com/Q/How_many_gallons_of_fuel_does_a_20-pound_propane_tank_hold

For your 100lb tank to cost $76, I calculate that as 23.5gal, or $3.23/gal. Is it possible you are paying a delivery charge? Or maybe its just a regional cost difference?

Thanks for all your help on my sanity check btw.

dkershner said:

If your 100lb tank costs .76/lb, I must be off on my calculation. I am using 20lb tanks and fill them at a gas station. It isn't a swap, it's a fill, just like you would a car. The current cost is around $2.10/gal at the ones near my house.

I pulled the figure of 4gals per tank from here: http://answers.yahoo.com/question/index?qid=20070616040854AAdKgt4
OR
http://wiki.answers.com/Q/How_many_gallons_of_fuel_does_a_20-pound_propane_tank_hold

For your 100lb tank to cost $76, I calculate that as 23.5gal, or $3.23/gal. Is it possible you are paying a delivery charge? Or maybe its just a regional cost difference?

Thanks for all your help on my sanity check btw.

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Well, like CO2 the gas volume is dependant on the pressure. That is why it is generally sold by the pound. For bulk propane to be sold by the gallon it must have a standard pressure at which it is dispensed. I dont know for sure.

It has been a while but the last time I filled a #20 tank I believe it cost me $18.00. That is where I got the .90 figure from. I live in a small town so cost may well be more here.

One way to know for sure how many pounds your tank holds is to weigh it empty (tare weight...may even be stamped on the tank and is usually about 18lbs for a 20lb tank) then weigh it after filling.

I like electric for my brewing. I plan to convert my kettle some day also. It is not easy to compare costs as there are so many variables but I do like not worrying about running out of propane. The upfront costs of electric are definately more and It may not be reasonable to try to recover the costs.

lschiavo said:

One way to know for sure how many pounds your tank holds is to weigh it empty (tare weight...may even be stamped on the tank and is usually about 18lbs for a 20lb tank) then weigh it after filling.

I like electric for my brewing. I plan to convert my kettle some day also. It is not easy to compare costs as there are so many variables but I do like not worrying about running out of propane. The upfront costs of electric are definately more and It may not be reasonable to try to recover the costs.

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I need a refill right now, I will weigh it before and after.

Thanks for all the input lschiavo, there are definite other benefits to electric to think about, but I guess it matters how much convenience matters to the individual.

dkershner said:

I need a refill right now, I will weigh it before and after.

Thanks for all the input lschiavo, there are definite other benefits to electric to think about, but I guess it matters how much convenience matters to the individual.

Click to expand...

No problem at all. If you haven't already, check out the electric build threads here. With all the details others have provided, I am sure you could build something yourself and you can go just as simple or complicated as you like.

Let me know what you find for your cost out of curiosity.

lschiavo said:

No problem at all. If you haven't already, check out the electric build threads here. With all the details others have provided, I am sure you could build something yourself and you can go just as simple or complicated as you like.

Let me know what you find for your cost out of curiosity.

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I am quite well versed on the systems around these parts. I might be able to get away with building one, but would rather rely on someone who is better than I am.

I used to wire cars in high school, and felt to force of DC through my body on more than one occasion. GFCI or not, I don't think AC is my friend. I did build a little waterproof outlet box for pump controls though.

It'll probably take me till this weekend to make it to the gas station, but when I do I will post back here.

OK, filled my tanks. Propane rose to 2.19/gal.

1st tank: Started at 17.0lbs, ended 36.5lbs. 4.71gal to fill = 19.5lbs
2nd tank: started at 18.5lbs, ended 36.5lbs. 4.3gal to fill = 18lbs.

Price per pound comes to .52.

I will edit my first post.

I switched from an electric water heater and dryer to propane. I estimate using propane is 2-3 times as expensive as electric. It was about even the first year but propane has gone way up. On the propane side, the dryer is much faster and when I lost power for 5 days in 2008, I still had hot water.

dkershner said:

OK, filled my tanks. Propane rose to 2.19/gal.

1st tank: Started at 17.0lbs, ended 36.5lbs. 4.71gal to fill = 19.5lbs
2nd tank: started at 18.5lbs, ended 36.5lbs. 4.3gal to fill = 18lbs.

Price per pound comes to .52.

I will edit my first post.

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That is a much better deal than I get on propane but there aren't many options around here. How does the cost alalysis look now?

BlueRino is the supplier in my area plus the EPA forced the max fill limit float you only get from 3.5 to 3.7 gallons if lucky to a 20# bottle. This At $23.95 exchange for 3.5 gallons on average or $6.84 a gallon. You tell me which costs more without adding your time and gas to get the damn propane bottle refilled? I refill my old style 20# bottles an honest 5 gallons off a family members 125 gallon propane tank at the ranch with my adaptor, this for the BBQ only. Been electric brewing over 6 years never looked back at propane.

lschiavo said:

That is a much better deal than I get on propane but there aren't many options around here. How does the cost alalysis look now?

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Looks like around here with cheap propane and relatively expensive electricity that it will basically never pay for itself. You would have to look at other benefits like automation and brewing inside to justify it. I myself don't care too much about brewing inside and don't really mind checking on the temps while having a homebrew, so I think we will be sticking with propane.

BrewBeemer said:

BlueRino is the supplier in my area plus the EPA forced the max fill limit float you only get from 3.5 to 3.7 gallons if lucky to a 20# bottle. This At $23.95 exchange for 3.5 gallons on average or $6.84 a gallon. You tell me which costs more without adding your time and gas to get the damn propane bottle refilled? I refill my old style 20# bottles an honest 5 gallons off a family members 125 gallon propane tank at the ranch with my adaptor, this for the BBQ only. Been electric brewing over 6 years never looked back at propane.

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You could just plug your numbers into the first posts calculations, but I would estimate the amount of brews is in the 100-200 range. Not unreasonable to achieve that in a few years.

Propane is so hit or miss, you literally need to do an analysis for yourself to see if the switch is worth it. Luckily here it is cheap, and 2 blocks from my house. No biggie for me.

dkershner said:

Looks like around here with cheap propane and relatively expensive electricity that it will basically never pay for itself. You would have to look at other benefits like automation and brewing inside to justify it. I myself don't care too much about brewing inside and don't really mind checking on the temps while having a homebrew, so I think we will be sticking with propane.

Click to expand...

Yeah, electric does have its merits for control. I love my HLT. It works great for me. I use an Auber temp controller with, 4500W element, high and low water floats, solenoid valves to fill and drain, a stir pump and HERMS coil installed. It cost a few bucks and was quite a bit of work to set up but I get dead on temps, it is pretty much foolproof, and I dont lift any brewing water until its in the fermenters.

I am in no rush to convert my boil kettle though. I like that it is not tethered to anything so I can easily take it to the sink for cleaning. I guess mine is a hybrid system now and may just stay that way.

lschiavo said:

Yeah, electric does have its merits for control. I love my HLT. It works great for me. I use an Auber temp controller with, 4500W element, high and low water floats, solenoid valves to fill and drain, a stir pump and HERMS coil installed. It cost a few bucks and was quite a bit of work to set up but I get dead on temps, it is pretty much foolproof, and I dont lift any brewing water until its in the fermenters.

I am in no rush to convert my boil kettle though. I like that it is not tethered to anything so I can easily take it to the sink for cleaning. I guess mine is a hybrid system now and may just stay that way.

Click to expand...

I would like to convert to electric just for the awesome control it provides, but the desire is not nearly great enough to switch over at this time. I have very little trouble with control and can actually not lift any brewing water EVER if I roll my setup a little closer to my ferment chamber, but it's not like the cornies I ferment in are that heavy and they could use a bit of shaking on their way over.

Good stuff lschiavo, thanks for the input.

dkershner said:

I would like to convert to electric just for the awesome control it provides, but the desire is not nearly great enough to switch over at this time. I have very little trouble with control and can actually not lift any brewing water EVER if I roll my setup a little closer to my ferment chamber, but it's not like the cornies I ferment in are that heavy and they could use a bit of shaking on their way over.

Good stuff lschiavo, thanks for the input.

Click to expand...

No problem! Happy Brewing

How does the cost work out if you augment gas with a heatstick?

wetherel said:

How does the cost work out if you augment gas with a heatstick?

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Figure out how many BTUs are coming from each. Electric is easy, use my equations. Gas is tougher, I estimated based on how many times it takes me to empty the tank.

dkershner said:

You could just plug your numbers into the first posts calculations, but I would estimate the amount of brews is in the 100-200 range. Not unreasonable to achieve that in a few years.

Propane is so hit or miss, you literally need to do an analysis for yourself to see if the switch is worth it. Luckily here it is cheap, and 2 blocks from my house. No biggie for me.

Click to expand...

A total ripoff in my area, hell it's a gold mine for Blue Rino as they have the S.F. bay area about fully covered. I used to refill 20# bottles off a 100 gallon propane tank until it got too heavy to load and get refilled plus past the hydro date stamp. Gave it away and went electric. I only go thru 2-3 20# for the BBQ and refill off a friends house heating propane tank which is a drop in the bucket vs his large tank, bier and some cash repayments works for both of us. The big issue will be the new "smart meters" coming to our area soon. Many problems with overbilling
so far. I'll add a spare meter to compare against it with a court battle if needed as I have 20 years of past records. Ask for them they claim no longer available.

BrewBeemer said:

A total ripoff in my area, hell it's a gold mine for Blue Rino as they have the S.F. bay area about fully covered. I used to refill 20# bottles off a 100 gallon propane tank until it got too heavy to load and get refilled plus past the hydro date stamp. Gave it away and went electric. I only go thru 2-3 20# for the BBQ and refill off a friends house heating propane tank which is a drop in the bucket vs his large tank, bier and some cash repayments works for both of us. The big issue will be the new "smart meters" coming to our area soon. Many problems with overbilling
so far. I'll add a spare meter to compare against it with a court battle if needed as I have 20 years of past records. Ask for them they claim no longer available.

Click to expand...

If I lived in SF, electric would be a no-brainer for me. Of course, then you have to worry about us running out of power and giving you guys brownouts.

dkershner said:

If I lived in SF, electric would be a no-brainer for me. Of course, then you have to worry about us running out of power and giving you guys brownouts.

Click to expand...

East of S.F.'s rat race concrete jungle on an island in the bay.
Gasoline alone is the highest in the country. Cost of living's also
high as well the quality of the neighborhood and schools. Trade offs.
We are the very few of of cities across the US that purchase power off the main grid not from
PG&E plus cheaper besides geothermal steam generating power plants, we're rather "green".

there are other factors involved:
-difference of cost of electric equipment vs propane equipment
then the difference in price divided by the savings price would be more realistic
which wouldnt apply to you due to you already having propane.
-electric is much better in colder temperatures, especially in colorado, when you don't have to leave the garage door open to vent exhaust.
-being able to flip a switch to turn get heat!

There is a MUCH easier way to calculate gas vs electricity. The problem is gas is rated in BTUs and electricity in KWh. Without going into the calculations I can tell you that 92,000 BTU's, the amount on one gallon of propane, is equivalent to 27 KWh of electricity when used for heat

So at 15 cents a KWH it is the same as $4.05 a gallon for propane. It depends on your electricity and propane costs, but that puts electricity at just about 2x the cost of propane. Not to mention propane will heat faster (you can get it hotter, using more propane) and produces FAR less emissions then coal (in case you were thinking it was more green). About the only advantage I can see to electricity is it can be used in a smaller space and is more convenient (well unless you do not like to use 8 gauge wire and 30A 240V circuits)

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.

Torg said:

There is a MUCH easier way to calculate gas vs electricity. The problem is gas is rated in BTUs and electricity in KWh. Without going into the calculations I can tell you that 92,000 BTU's, the amount on one gallon of propane, is equivalent to 27 KWh of electricity when used for heat

So at 15 cents a KWH it is the same as $4.05 a gallon for propane. It depends on your electricity and propane costs, but that puts electricity at just about 2x the cost of propane. Not to mention propane will heat faster (you can get it hotter, using more propane) and produces FAR less emissions then coal (in case you were thinking it was more green). About the only advantage I can see to electricity is it can be used in a smaller space and is more convenient (well unless you do not like to use 8 gauge wire and 30A 240V circuits)

Click to expand...

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.

Brewmoor said:

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.

Click to expand...

It would most likely be less. Using a duty cycle controller you may only need to set the element at 60% to maintain a boil. That would put you around 3.3 kWh. Of course you would be full on to get to boiling.

lschiavo said:

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.

Click to expand...

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.

Brewmoor said:

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.

Click to expand...

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.

Torg said:

Many are only about 75% efficient

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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?

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.

dkershner said:

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.

Click to expand...

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

lschiavo said:

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

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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.

lschiavo said:

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?

Click to expand...

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.

dkershner said:

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.

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

lschiavo said:

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

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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.

Torg said:

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.

Click to expand...

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.