A question that comes up a lot when home brewers are looking to purchase a propane burner for boiling wort is how many BTU do I need to get the job done? If you’ve spent any amount of time looking at burners, you’ll quickly see that the BTU output can range from 50,000 all the way up to 200,000+, so it can be confusing when trying to determine what you really need.
For the purposes of this blog post, let’s assume you are trying to boil a 10-gallon stockpot or wort. We know that that average household stove ranges anywhere from 7,000-9,500 BTU, and this simply isn’t hot enough to boil 10-gallons in any reasonable period of time.
So lets take a look at what we will need. With a little help from Wolfram Alpha, we can figure out what we will need at a minimum.
First we need to see how much energy is needed to boil 5 gallons of water:
Through this calculation, we see that it will require 48200 kJ (kilojoules).
Since we are looking for BTU, we need to convert kJ to BTU which we can also do with Wolfram Alpha:
After running the conversion, we see that the result is approximately 45,000 BTU.
While these exact calculations are nice, they don’t necessarily translate to real-world scenarios. Here are some more rough approximations that we have found to hold true.
5 gallons of wort will require at least 55,000 BTU
10 gallons of wort will require 100,000 BTU
15+ gallons of wort will require 200,000 BTU
Here is the basic gist of it: Any commercially available propane burner will be able to handle a 5-gallon pot or wort. As you go bigger, if you will want it to boil in roughly the same time, you will need to go hotter. The BTUs of burners, roughly speaking, make the jumps outlined in bold above so when you go up 5 gallons, make the jump to the next BTU tier.