HX vs Double Boiler Espresso Machine - Pros and Cons

Recommendations for buyers and upgraders from the site's members.

#1: Post by BaristaMcBob »

I understand how the two systems are different, from a design perspective. What I don't understand are the pros/cons of each and was hoping someone could explain in simple terms.

User avatar

#2: Post by HB »

Dan Kehn

User avatar

#3: Post by slybarman »

My $.02, the only downside to a DB is up-front cost and maintenance (2x boilers).

Upside is much easier workflow and better consistency.

If you can swing it cost-wise, DB is a no-brainer in my book having owned both.

Machines like Lelit's MaraX, somewhat blur the line in terms of workflow and consistency, but it is a cost compromise, so I come back to to DB if you can.

BaristaMcBob (original poster)

#4: Post by BaristaMcBob (original poster) »

Thank you for reference. They said the main drawback to HX, according to the video, is the need to pre-flush. However, my Bezzera BZ10 HX machine doesn't have that problem. My brew water is always the right temp. I don't get a blast of steam if I pre-flush as the machine in the video did. My other machine, ECM with an E61, doesn't release a "dragon" either. So maybe that's an issue with some HX machines and not others? IDK.

I wish they had demonstrated steaming power. Very informative video otherwise.

BaristaMcBob (original poster)

#5: Post by BaristaMcBob (original poster) »

Hi. Thanks for the comment. Can you elaborate on what you mean by an "easier workflow?" The basic process seems to be identical for both types of machines.

User avatar

#6: Post by HB »

Temperature management for double boilers is pretty straightforward; two second flush and you're ready, if that. With a heat exchanger, the idle time and pace that you make drinks very directly impacts the brew temperature. Ideal brew temperature management elaborates on this point. Manufacturers have gotten better about tuning "no fuss" heat exchangers for home-friendly usage (i.e., walk up and/or a slow pace).

All other things being equal, a heat exchanger espresso machine will be cheaper than a double boiler; obviously the former will have less parts, which means manufacturers can add more bells-n-whistles while keeping a desired price point (e.g., joystick steam wands instead of knobs, nicer portafilters).

By the way, this question has come up many, many times before. The video I posted above summarizes the opinions that I've garnered over the years. There are some baristas who feel managing an HX espresso machine is no big deal (I agree that's true for many cases) while lots of others just don't want to deal with the extra work. The analogy I often use is manual vs. automatic transmissions in sports cars. There are some who want the experience of "rowing the gears"; others see that as pointless effort. In my opinion, neither group is wrong.
Dan Kehn
★ Helpful


#7: Post by yyacoob »

2 more cents. If you are more for espresso than frothing, 2 boilers is a great waste. You make your balance point, personally I think anywhere 80%+ espresso, HX is it. Beyond utter waste, there is the practical point that HX used for mostly espresso will spare you descaling and boiler issues. I looked into my ECM boiler after 6 years of use of 95% espresso and it looked brand new (and I don't use any water treatment other than a regular filter). My ECM HX was not as good as I wanted back when 5% was frothing, but with 0% frothing it is no brainer to me. In fact I can't wait for no-boiler espresso machines.

Finally, a flush is so natural, you will want to clean the screen anyway! I would flush even with a double boiler...

User avatar

#8: Post by slybarman »

why not go single boiler then at that point, no HX?

User avatar
Team HB

#9: Post by another_jim »

A bit of not so boring history: Twenty years ago, on alt.coffee, we used to argue this forever. Double boilers were more costly and less efficient; HX machines were crap shoot shot makers, all over the place. Oddly enough, the on-line world of hobbyist espresso and barista competitions is what changed this.

-- The first realignment was the NS Aurelia, a numerically modelled HX machine with zero electronic parts. Greg Scace was doing contortions trying to get it not to come out at exactly 93C -- he could let it sit and jump on it, let it run for a minute, it didn't matter (warning: this was a machine directly from their engineering department for the first WBC, no idea if a regular Aurelia is this good).
-- Gicar making standardized PID controls, now ubiquitous on all Italian espresso machines was part of the next step. Eric's thermometer for E61 boxes was part of it too. A VBM or Isomac from 2002 had to be flushed for ages to get to temperature. Most HX E61s now are far better tuned. Manufacturers are actually paying attention to stable temperatures in all their offerings. For instance, nowadays, you can get cheap PID thermoblock machines that outperform most expensive home machines from twenty years ago. The final step was lightweight groups with included heaters, or electrically heated groups coupled to HXs. There are now a far larger number of designs variations than just HX or DB.
-- The come back of lever machines and flow controlling is the most recent step.

Given these developments; I no longer think that DB versus HX is a big deal -- there are all sorts of new design wrinkles that make a difference. I think there's been more variation and change in espresso machine design in the last twenty years than in the 40 years before that. From E61 to alt.coffee was one era; on-line espresso is the new one.

For machine buyers -- look closely at the actual specs, look for expert user reports, and put you buzzword cheat sheet back in the drawer.
Jim Schulman

BaristaMcBob (original poster)

#10: Post by BaristaMcBob (original poster) »

Thank you for that very helpful perspective. I remember alt.coffee. Those were my Gaggia & ESE Pod years.