Cost of Energy to Produce 5 gallon batch:
Let me set the stage for you. I love the idea of converting my system over to electricity. As I read the posts on this site I am amazed at some of the backgrounds on here, Mechanical Engineers, Electrical Engineers, Chemists and the list goes on. My background is finance…in other words part of the fun in this hobby for me is the cost of things and how can I produce something as cost efficiently as possible. I think we would all agree once we start adding our respective incomes on an hourly basis – the cost of goods sold line in the income statement would change dramatically. Nonetheless, this thought process led me down the rabbit hole to see if I could try and figure out the economic viability of changing my system over to electric to bring my cost per beer down. Might also serve as an argument to the wife why I should spend 2k upgrading service, equipment, etc. Enough of the background, let me get on with the experiment.
Some of the base information: I live in Southern California, which means my electric service comes from Southern California Edison, my Natural Gas service comes from So Cal Gas and my propane is provided by Camping World just down the street.
Current Cost of Energy:
1 kWh from SCE = $0.21 (average cost over the tiers that we use)
1 Therm of Natural Gas = $0.72/.85 (NG is 15% less efficient than propane) = $0.85 (rounded up)
1 Therm of Propane = $3.34 (1 gallon of Propane = 91k BTU’s @ $3.67 gallon / 100k)
A few quick conversions of kWh to therms:
1 kWh = 3,414 BTU’s: 100k BTU’s = 1 therm: 100k/3,413 = 29.3 kWh: 29.3 kWh = 1 therm
Step One: Conversion to standard measure of energy cost
Natural Gas: $0.72/therm
Electricy: 29.3 kWh * $0.21 = $6.15/therm
Step 2: Convert 8 gallons of water from 60* to 160* (strike temp)
Need 1 BTU to raise 1# of water 1*F; Water weighs 8.34#/gallon
8 gallons * 8.34# = 66.72# of water
66.72 * (165*- 60*) = 7,005.6 BTU’s needed to raise 8 gallons of water from 60 degrees to 160 degrees
7005.6/100,000 = .0701 therms
Cost to raise water to strike temp (highest to lowest)
kWh: 0.43; LP: 0.23; NG: 0.06
Step 3: Bring Wort to a Boil (I am at elevation water boils at 210)
(210 – 152 mash temp) = 58* x 66.72 weight of water = 3,869.76 BTU’s needed to boil
Cost = kWh: 0.24; LP: 0.13; NG: 0.03
Step 4: Maintain boil for 60 min
Admittedly, this is where I ran into a bit of an issue, and perhaps where the math may fall apart a bit. I had a difficult time coming up with a formula to calculate heat loss and reduced energy needed to maintain a boil once reached. Therefore, I went with 60%. Why 60%. I have seen numerous times on this forum, where brewers will set there PID’s to a 60% cycle setting. That is what I went with.
Using a 5500w element, running for 60 min to calculate energy used.
5500 * .6 = 3300w / 1000 = 3.3 kWh * 3,413 (conversion factor of kWh to BTU) = 11,263 BTU’s
11,263 BTU’s / 100k = .1126 Therms * $6.15 = $0.70 to maintain a boil for 60 min.
.1126 therms (from above calc) * $0.85 (cost of a therm) = $0.10 (rounded up)
.1126 therms * $3.34 = $0.38
TOTAL COST OF ENERGY TO BREW A 5 GALLON BIAB BATCH:
kWh = $1.37
LP = $0.74
NG = $0.19
I need to come up with another angle to sell the conversion to all electric to the wife, the math isn’t gonna do it!
On a somewhat more serious note, I would like to think I thought through this pretty well. I had to make a few assumptions here and there. Nonetheless, it was a fun exercise doing the conversions and just seeing how expensive electricity has become in So Cal. Not to mention seeing how much energy is required to complete certain tasks. By the same token, how inexpensive Natural Gas has become. If I were to purely make decisions only on the math, there is no discussion, I could easily argue I should run a natural gas line to where I brew and doing everything on Nat gas. Further, I should look to convert over to Nat Gas fired electricity. I did not take into consideration heat loss to pots, ambient temp, and yes I know those will play a role. However, when you look at the disparity in cost, there is no way whatever inefficiencies there might be with NG it is highly unlikely in my opinion they will overcome the expense of electric. That said, time to convert to all-electric, why? Just too cool not to!