A lot of customers have asked over the years how many watts of power they need for their electric brewery. I've been able to give estimates based on the actual BTUs needed to heat water + 30% for loss, but my answer has never been exact. So, when I finally sat down and calculated real world losses I decided to use a converted beer keg or keggle because they make a great brew pot & a lot of 10 gallon brewers use them. Keggles hold 14.5 gallons of beer which makes them the perfect size for a 10 gallon batch.

To calculate BTUs needed and heat loss we need to start with the basic stats:
30# - Weight of a empty beer keg
16.5" - Keg diameter
23.3" - Keg height
12 gallons - Batch size these calculations are based on
0.12 BTUs - to heat one pound of steel 1 degree F
3.6 BTUs - to heat the keg 1 degree F
8.34 BTUs - to heat one gallon of water 1 degree F
1.5 sq ft - Water surface area of keg
8.38 sq ft - Side surface area of keg
1.5 sq ft - Bottom surface area of keg
3.41 BTUs - Heat generated by one Watt/hr of electricity

Then I found the standards above in a published Engineering table. The table lists BTU/hr loss per square foot in a steel tank with no insulation, assuming the temperature outside the tank is 70F.

Thanks, Tom
Find more electric brewery tips at www.kegkits.com

Step 1: BTU Losses during Brewing

So, using basic stats & the Engineering Table I found, I can calculate heat loss in BTU / hr, assuming you are boiling 12 gallons of water. The resulting graph has the temperature across the bottom and the loss along the left side.

The first thing you probably notice is the fast growing yellow line - all the way to 9000 BTU / hr at 210 F. This is also close to the BTU / hr you will need to maintain a boil.

The next thing you probably notice is the fast growing blue line - this is loss due to evaporation. And this heat loss is easy to prevent by keeping the lid on your hot liqour tank and boil pot will make a huge difference!
Very informative, I knew none of this when I built my station, but the 5500 watt was the biggest element I could find so that's what I installed...