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December 12, 2017
Last updated

All Electric Brewing - Boiling Wort

Owner of Clawhammer Supply

The biggest consideration with all electric brewing systems is the impact of the available power. Any system that can be plugged into a standard 120v, 15 amp outlet (your typical power outlet in the U.S.) is that the maximum available wattage will be 1650. See our article on brewing 5 gallon batches with 120 volts for a very detailed write-up on this topic.

In order to achieve a boil on 1650 watt homebrew systems, the a lid must be utilized in a way that covers up most of the kettle opening. If you've read virtually any book on making beer, you'd be led to believe that this is homebrew suicide. Most resources state that low hop alpha-oil isomerization and DMS production will be certain to ruin your brew. But is this true?

We've done a lot of research and testing on brewing and boiling with 1650 watt elements and our conclusion is that the dangers of boiling in an insulated brew kettle with a mostly covered kettle are nothing more than urban legend. Here's a breakdown of what we've discovered.

The Importance of Boiling Wort

First, here's a quick summary of why boiling "wort" (what you call beer after mash but before fermentation) is a very important part of the brewing process. Boling wort accomplishes the following:

  • removal of DMS,
  • isomerization of hops,
  • sterilization,
  • and liquid volume reduction (boil off).

Following is a quick summary of the research and testing we’ve completed regarding beer quality as related to boil vigor and method (lid on but cracked).

Removal of DMS

Dimethyl sulfide (DMS) is a byproduct of S-methylmethionine (SMM). Without getting too complicated, SMM is produced during the germination of barley (at the beginning of the malting process). When SMM is heated it begins to break down into DMS, which tastes like overwhelmingly like corn, which isn't generally isn't a good thing.

However, when wort is boiled the DMS is driven away because it has a lower boiling point than water. In fact, the boiling point for DMS is 99F. That's more than 100 degrees Fahrenheit lower than the boiling point of water. So, if your beer achieves even a very weak boil you're driving off all the DMS you need to drive off to make it a non-issue in your final product.

Our research and experience indicates that even an extremely weak 60 minute boil eliminates DMS without a problem. Additionally, almost completely covering a kettle to achieve a more vigorous boil also eliminates DMS, so long as there is at least a small opening for steam to escape.

Isomerization of Hops

Isomerization of hops is the process of turning alpha acids in hops into iso-alpha acids. This creates bitterness in beer and happens during the boil. Isomerization is a non-linear process, meaning it happens at different rates depending on temperature. In short, higher temps and longer boil times equals a higher conversion rate of alpha acids to iso-alpha acids which equals more bitterness.

When using 10 gallon electric systems on 120V circuits, brewers should be cognizant that weak boils will produce slightly lower levels of iso-alpha acids. This, however, will have much less of an impact on hop flavor and aroma, as flavor and aroma are released into the beer much faster. Sometimes too fast!

Our research and experience indicates that to achieve a specific bitterness level, brewers may want to add slightly more hops (or add them earlier) if the system produces a low boil. Adding a bittering hop with a higher alpha acid % will increase bitterness as well.


Boiling wort kills bacteria that could potentially contaminate and ruin good batches of beer if not neutralized.

According to updated guidelines and studies released by the Center for Disease Control (CDC), World Health Organization (WHO) and similar agencies, water is typically sterilized and suitable for brewing by the time it reaches a boil.

Because boiling takes place at various temperatures depending on elevation and atmospheric pressure, water does not need to reach 212F to become sterilized for brewing. So, a low boil will not have an impact on sterilization.

Liquid Volume Reduction (Boil Off)

Liquid volume reduction, or boil off, increases starting gravity by concentrating the sugar (and flavor) in wort due to the evaporation of water.

Every brewing system, whether that be a small personal system or a large commercial system, will have a different boil off rate depending on the system's design. The boil off rate and corresponding reduction of liquid volume will obviously be lower on kettles that utilize a partially cracked lid to increase boil vigor. 

To account for the change in boil off rate, simply boil a test volume of liquid over a set period of time, note the liquid reduction, and plug these results into the program that is being used to generate targets (i.e. Beersmith).  

Kyle Brown is the owner of Clawhammer Supply, a small scale distillation and brewing equipment company which he founded in 2009. His passion is teaching people about the many uses of distillation equipment as well as how to make beer at home. When he isn't brewing beer or writing about it, you can find him at his local gym or on the running trail.

  • Hallo Kyle.

    I find your system of boiling the wort very interesting, it must be intense but in a short time (no less than 40 minutes). CHEERS from Peru.

    Posted by Walter Prötzel on November 08, 2023

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