boil off rate of a keggle

Does anyone have a ballpark figure on the boiloff rate on a keggle over an hour?

I would assume it would be around the standard rate - around 9%-15% per hour. Once the wort is boiling, the evaporation rate is based on the surface area exposed... although I'm sure the style of keg and size of opening would affect the rate slightly.

I'm curious... does gravity affect evaporation rate. It seems that higher gravity wort would boil at a higher temperature, meaning that water would turn into vapor more quickly. Any thoughts? (sorry to piggy back BeerPressure)

I get just over 10% but I live in southern IL so the weather is usually humid

I boil off about 1.5g per hour. 4500 Watt electric elment set to 80%

Well, boil off cannot be calculated as a %... since it is a constant and %ages are not constants.

That being said, I boil off about 1.4 gallons per hour with 3800W of electricity going into my kettle. This was about what I got when I used an LP burner too.

Wind speed, humidity, surface area (though we are talking keggles so that is pretty standard here) and other factors will AFFECT the boil off rate, but not to a measurable degree on a HB scale


I start with say 7.5 gallons and boil off 1.4 per hour, so that is almost 19%, if you want to use a percentage... (but why???) And why is 9-15% standard?

Pol, quit being difficult.

I'm sure he's just trying to work out some standard calculations or plug that number into some brewing software. You can use a percentage, but it's got to be over a specified time period. I think 10-15% evap over 1 hr is pretty standard with a nice rolling boil.

I plug 11% into beersmith and it works out well for me.

Lil' Sparky said:

Pol, quit being difficult.

I'm sure he's just trying to work out some standard calculations or plug that number into some brewing software. You can use a percentage, but it's got to be over a specified time period. I think 10-15% evap over 1 hr is pretty standard with a nice rolling boil.

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Untrue...

You will always boil off (within reason) the same amount per hour, as a constant. A % will change with volume. That is the whole story.

10% of 12 gallons is 1.2 gallons
10% of 6 gallons is .6 gallons

You dont boil off twice as much when you double your batch size.

I agree with Pol again..sheesh. I boil off 1.5 gallons per hour running about 70kbtu. It's the same whether it's 6 gallons or 12.

I said standard because almost any source that I have seen gives you somewhere in that range. I guess it is pretty much tied to batch size and should be stated that it is 9-15% for a ten gallon batch with a 60 min boil. And, a 60 min boil is (dare I say it...) pretty standard also. I guess it is more correct to state the boil-off amount as a volume/hr. Although, if you want to be picky, there are several conditions that will affect the boil-off rate including humidity, atmospheric pressure, temp of water and air, surface area and air movement around the vessel.

My original answer should have been:

The boil-off rate will be specific to your set-up. Develop some good measuring techniques and just do an experiment over a couple of brewing sessions. That way, you will know your specific boil-off rate.

Oh shnazzle, I've been trumped. What the smart guys said.

I made a 10gal Oktoberfest, 90-95 deg day.

65000BTO turky fryer
Sanke Keggle

Preboil was 12.5gal final was 10.25gal

Grizzlybrew said:

The boil-off rate will be specific to your set-up. Develop some good measuring techniques and just do an experiment over a couple of brewing sessions. That way, you will know your specific boil-off rate.

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+1! Learn your rate. Keep a logbook. You will eventually know very accuratley how much to expect based on that day's temp/humidity. We can only give you a ballpark, which will probably be 1.5-2.5gal/hour

Also, the size of t burner doesnt matter, since I have never met anyone that boils with thier burner at 100%

13,000 BTUs directly into my wort gets me 1.4 gallons of boil of per hour on a "typical" day

I'm just looking for a starting point. Ive got a keggle and I'm gonna enter it into the equipment database in beersmith and just need somewhere to begin.

BeerPressure said:

I'm just looking for a starting point. Ive got a keggle and I'm gonna enter it into the equipment database in beersmith and just need somewhere to begin.

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From my experience, 1.5 gal/hour is a good starting point.

The Pol said:

Untrue...

You will always boil off (within reason) the same amount per hour, as a constant. A % will change with volume. That is the whole story.

10% of 12 gallons is 1.2 gallons
10% of 6 gallons is .6 gallons

You dont boil off twice as much when you double your batch size.

Click to expand...

I'm, obviously, opening myself up to ridicule by reviving this old thread and calling out a "senior" member...but my God...The Pol (who, as I take it, has abandoned the forum) really comes off as smug and intolerant prick in MANY of his posts across a great many threads. I know he's provided a wealth of information to this forum, but...really...why so condescending?

I have to shell out props to members like Sparky and Bobby, et al., who consistently offer NON-condescending advice to all of the more inexperienced members on the forum (me included).