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# Estimate Energy Usage per Charge Size

edited July 2016

Could anyone point me to a read or formula for trying to estimate kWh for a run? I've got a 26 gallon still and a 4" ProCap column and will be heating with 2x 4500W elements. Going from 60°F to boil hopefully in an hour and then taking it off at a medium pace with SSRs.

I'm looking at trying to get a COGS - electricity line item that roughly correlates to the size of the charge, so if I wanted, could estimate up-sizing to a 100 gallon still.

Overestimates are fine as long as they are not way off. If it comes out cheaper to run it - all the better!

This was my first stab by using water, as I could find the coefficient for water heating by 1 degree easily from hyrdonic heating websites:

``````0.0024444 Kwh to raise 1 gallon of water 1°F
0.293328  kwh to raise 120 degrees
35.19936  120 gallons
\$0.30     \$ / kwh (guess)
\$33.00    electricity cost for initial heat up
(SSR for maintaining temp so I assume there is more to this)
\$66.00    double for good measure => COGS electricity / batch
``````

Am I totally off?

Tagged:

• edited July 2016

35kwh to heat up at 30 cents is only \$10.50. 30 cents seems high unless you are somewhere like Hawaii. Doubling the heat up cost is probably in the ballpark.

• Sorry for the formatting issue. I tried to fix it, but it's still a bit off.

Yes, \$0.30 is high. We are tiered up here in VT after 200 kwh it jumps to 0.22 for residential. I will call and get those numbers more definitive tomorrow.

Does the kwh usage/method of estimating kwh seem like it is in the ballpark?

• I think you're over complicating. Should only be a couple of bucks.

2 x 4.5 kW x 1h = 9 kWh for heat up
1 x 4.5 kW x 3h = 13.5 kWh for the run (assuming 5% wash, 75% ABV collection, and about 3h run time)

\$.33 / kWh sounds high. Local here is around \$.18.

And as you're most likely storing your product for a bit, it would go in your COGM

• OK, like the simplicity.
COGM stands for manufactured?

• I agree with Unsensibel's approach: 1. work out your heat up time - multiply that by the element power (kW) you are using for heat up by the cost (\$/kWh). 2. work out your run time - multiply that by the element power (kW) you are using for the run by the cost (\$/kWh).

Or if you want some fat in your figures, work out the total time (heat up & run) multiply that by the total element power available by the cost

• Understand that if you are running any sort of reflux condenser, the only energy that correlates to product output is the difference between power input and the energy taken out of the system by the reflux condenser. For example, at 100% reflux, that net product energy is zero. Your energy/product output approach only works for a (well-insulated) pot still.

Zymurgy Bob, a simple potstiller

my book, Making Fine Spirits

• edited July 2016

\$.30/kWh is cheap for purchased power in HI. Think > \$.40/kWh (fluctuates with price of oil). Payback period for PV is pretty short there.

I'm more like I am now than I was before.

• ZB,

Yes you are right that in your example the "net product" energy is zero, however the power going into the boiler costs real \$ as does cooling water / pumps etc.

Just like sitting at the lights in your car with your feet on the brake and holding the accelerator to the floor costs you \$ in terms of fuel consumed, holding your still at 100% reflux will also cost you.

I believe that the original poster is trying to work out the cost of production by adding all the variable costs that go into making something such as raw ingredients, water, labour, filtration media, barrels, bottles, labels etc etc.

Power in the form of electricity consumed during heat up and operation is just another one of these costs.

• edited July 2016

Just a note, losses due to the SSR are inconsequential, the losses from a non-insulated boiler would be greater. Either way, you are probably talking about less than a dollar difference at the 120g level.

I'd say you are probably looking at like \$15-20 a run, give or take. By the time you divide that into the bottle cost, it's going to be a couple pennies differential.

We burn a couple of gallons of oil a run, I think the last time I calculated, about 8-9 gallons, at 2.10 or so a gallon, that's about \$19 a run - and I'm 1000 liters boiler size. About 1/3rd of the cost of \$0.22/kwh electric? It converts to about 369kw input energy (into the oil burner, not the still), which would cost an astronomical \$110 at 30 cents a kwh, realistically less since electric is more efficient, but it's not THAT much more efficient).

Keep those rigs pumping baby.

• @mtnspirits said: OK, like the simplicity.
COGM stands for manufactured?

Correct. It's managerial accounting splitting of hairs ;)

Check your local utility for the rates. I just rechecked mine and it comes to about \$0.13-\$0.18 depending on the time of day.

On the reflux/loss comments, here's my take: You can do all kinds of estimations with theoretical losses and such but to me, it boils down to how much you're firing the element & how quickly you're taking off. While I haven't fired 100gal (yet), I typically equalize and collect between 50%-60% power, then drive the output ABV/speed through the RC.

• edited July 2016

It all depends on many variables but this might help

• edited July 2016

@crozdog said: Yes you are right that in your example the "net product" energy is zero, however the power going into the boiler cost Just like sitting at the lights in your car with your feet on the brake and holding the accelerator to the floor costs you \$ in terms of fuel consumed, holding your still at 100% reflux will also cost you.

Of course I was just using 100% reflux as a boundary condition, but it means if you are using 80% reflux, then 80% of you power cost is going out with the reflux condenser water, a loss that's non-existent in a pot still. Also running at 100% reflux is necessary for a while just to establish equilibrium, again, not a potstill issue.

Zymurgy Bob, a simple potstiller

my book, Making Fine Spirits

• edited July 2016

The reflux thing is complicating this question, but it boils down to this.

If you undersize your column (diameter and plates) to save money, you end up having to run it slower, and longer, this translates into significantly more energy being used.

On the hobby side, it probably doesn't matter.

On the commercial side, you could have probably purchased a more appropriately sized column (diameter and plates) or the money you'll burn in additional electrical usage in your first year, especially if you are closer to \$0.20c than \$0.10c. Likewise with steam, the ROI is probably around 2 years.

• so if we pump the right refrigerant in a loop and have the boiler be the condenser and the RV be the evaporator....