Hamilton Beach Flexbrew vs Keurig K Duo

This is my comparison of the Hamilton Beach Flexbrew vs Keurig K Duo, two combination K cup and drip coffee machines.

I own the Keurig K Duo and spent six hours watching product demos, reading reviews and pouring through the instruction manual of the Hamilton Beach Flexbrew to create this comparison.

Since the Keurig K Duo is typically more expensive than the Hamilton Beach Flexbrew, I’ll pay particular attention to whether for former machine can justify this additional cost.

Should I Buy the Hamilton Beach Flexbrew or the Keurig K Duo (Quick Answer)?

You should buy the Hamilton Beach Flexbrew over the Keurig K Duo. The Keurig K Duo offers a few advantages over the Hamilton Beach Flexbrew to justify its additional cost. The Hamilton Beach Flexbrew can create a greater range of coffees than the Keurig K Duo, including single-serve coffees without K cups, which the Keurig K Duo can’t make.

Advantages of Keurig K Duo:

  • More intuitive control panel
  • Makes better K cups due to the strong button
  • Lower maximum height so better for kitchens with low cabinets

Advantages of Hamilton Beach Flexbrew:

  • Allows you to make single-serve coffees without a K cup
  • Cheaper than Keurig K Duo
  • Fewer reported technical issues than Keurig K Duo

Although I believe that the Hamilton Beach Flexbrew is a better machine than the Keurig K Duo, there are still a couple of circumstances where I would recommend purchasing the Keurig K Duo over the Hamilton Beach Flexbrew.

These are:

  1. If you are going to primarily drink K cups: The Keurig K Duo is the better machine for K cups because it allows you to brew single-serve coffee with its “strong” setting mode. This brews the coffee for longer, resulting in a more flavorful K-cup drink.
  1. If you have low cabinets: The lid-up height of the Keurig K Duo is almost an inch and a half shorter than the Hamilton Beach Flexbrew. This can be all the difference between your coffee machine fitting snugly under your cabinets and you having to awkwardly pull the machine out of its spot when you use it. If you have between 17-18 inches of clearance between your counter and cabinets, opt for the Keurig K Duo.

You can find out more about the Keurig K Duo in my Keurig Duo review and Keurig Duo Plus review.

There are far more similarities than differences between these two products, but their subtle differences can greatly affect their utility to you depending on what you want from your coffee maker.

Let’s go through what sets these machines apart in more detail.

Features and Functionalities

Here is a breakdown of what the two coffee machines can actually do.

Types of Coffee

Although both machines make both drip and K-cup coffee, the Hamilton Beach Flexbrew offers you a wider range of coffee types than the Keurig K Duo.

This is because the Hamilton Beach Flexbrew allows you to brew single servings of drip coffee without K cups. 

The machine allows you to remove the K cup port from the single-serve side of the machine and replace it with a small, mesh drip coffee basket (this basket comes with the machine).

I absolutely love this feature because it allows you to brew single serves with a much higher coffee-to-water ratio than K cups allow for. 

The downside of K cups is they often come out watery because the coffee-to-water ratio is too low. This can completely mitigate that problem.

Winner: Hamilton Beach Flexbrew

Serving Options

One of the main differences between the two coffee machines is that the Keurig K Duo offers you pre-programmed serving sizes whereas the Hamilton Beach Flexbrew uses whatever water you put in its reservoir for each coffee that it makes.

With the Keurig K Duo, you have the options of 6 oz, 8 oz, 10 oz and 12 oz K cups and 6 cup, 8 cup, 10 cup, and 12 cup drip coffees.

The Hamilton Beach Flexbrew allows you to make single-serve coffees up to 14 oz and drip coffees up to 12 cups. 

Again, unlike the Keurig K Duo, the Hamilton Beach Flexbrew requires you to measure out the water you need for each coffee that you brew. I’d therefore recommend getting your hands on a measuring jug if you opt for this machine.

Winner: Hamilton Beach Flexbrew

Brew Strength Options

Both machines have a “strong” setting (called the “bold” setting on the Flexbrew) that makes the machines brew the coffee around 25% longer.

The key difference between the “strong” settings on the two coffee machines is that with the Keurig K Duo you can only brew K-cup coffee with the “strong” setting applied.

The Hamilton Beach Flexbrew only lets you brew drip coffees on the carafe side in “bold” mode.

I find it strange that neither coffee maker lets you brew all coffees in strong mode. 

From experience, hitting the “strong button” on the Keurig K Duo does improve the K cup coffee it produces quite significantly. 

Digging through customer feedback on the Hamilton Beach Flexbrew, people seemed to say that the bold mode did not make too much of a difference to the flavour of the carafe drip coffee. 

I suspect that this is because additional brewing time only really affects flavour if the brew temperature is correct.

Most filter coffee machines struggle to brew large quantities of coffee at a hot enough temperature, due to the quantity of water that needs to be heated. Therefore additional brewing time will enhance the flavor of larger servings of coffee less than smaller servings.

Winner: Keurig K Duo

Other functionalities

Both the Keurig K Duo and the Hamilton Beach Flexbrew have an automatic function that allows you to make a carafe drip coffee (but not a single serve) at a preset time in the next 24 hours.

Both machines also have a hot plate for the carafe that stays on for two hours after the coffee is brewed.

If you want to find out in more detail what the Keurig K Duo can do, please see my Keurig Duo review.

Overall Features and Functionalities Winner: Hamilton Beach Flexbrew

The features and functionalities of these two coffee makers are very similar, however, I love the fact that the Hamilton Beach Flexbrew allows you to make single-serve coffees with loose grounds as well as K cups.

Ease of Use

I’m going to break down ease of use into three components:

  • Ease of loading coffee and water
  • Ease of programming 
  • Ease of cleaning

Ease of Loading the Machine with Coffee and Water

Both machines are loaded up with coffee grounds/K cups in the same way. I’ve never had a problem with loading up my Keurig K Duo with coffee, nor have I read of anyone having difficulties loading up the Hamilton Beach Flexbrew with coffee.

As mentioned earlier, the two machines take water differently. 

The Keurig K Duo has a removable reservoir that holds 60 oz (12 cups of water). This water is dispensed according to the serving that you programme the machine to make. 

The Hamilton Beach Flexbrew does not have a removable reservoir, but rather it has two permanently-attached reservoirs that need to be filled with your desired amount of coffee each time. This creates another step in the coffee-making process.

Although its detachable, somewhat-automated reservoir may appear to make the Keurig K Duo more convenient to use, this is actually not the case. The Keurig’s reservoir system is so poorly designed that it is harder to use than the Hamilton Beach Flexbrew’s simpler system. This is down to two reasons:

  1. The Keurig K Duo’s reservoir is fitted to the back of the machine (see photo below). As it slots into the machine vertically, you need to get your arms over the machine and lift the reservoir vertically upwards to detach it. This can be awkward if you have limited vertical clearance above your machine.
  1. The Keurig’s reservoir was designed with a very thin, deep cuboid shape and there is little vertical room between its max line and the top of it. This makes it difficult to carry when full without water sloshing around and being spilled. Therefore I prefer to just fill it up with another vessel (usually a measuring jug).
The Kerig K Duo’s reservoir is fitted to the back of the machine and needs to be lifted vertically to be removed. This is awkward to do so I prefer to just fill it with a jug.

In short, a poorly designed reservoir means that the Keurig K Duo’s ability to store additional water to what it needs for a particular brew doesn’t actually offer any real benefits to the user over the Hamilton Beach Flexbrew.

Winner: Keurig K Duo (but not by as much as you’d first think)

Ease of Programming

Both machines use a buttoned control panel for programming the type of coffee that you want. However, the Keurig K Duo’s control panel and workflow are better designed and more intuitive than the Hamilton Beach Flexbrew’s.

The Keurig K Duo’s control panel is the best thing about the coffee maker.

Its intuitive design comes from the fact that each function has its own dedicated button and that any “eligible” button during your programming journey flashes so there is no confusion over what to do next.

Each feature on the Keurig K Duo has one dedicated button making it super easy to programme

It’s ridiculously easy to programme.

The Hamilton Beach Flexbrew is trickier to programme. Its more advanced features like auto brew are particularly fiddly to set up, with you having to hold down buttons for certain lengths of time and double tap buttons quickly. You can find a video of someone struggling with this here

The machine would have benefited from having a dedicated button for each function like how the Keurig K Duo has.

Winner: Keurig K Duo

Ease of Cleaning

Both machines have removable filter coffee and K cup ports and drip trays that can be cleaned separately from the machine.

The Hamilton Beach Flexbrew’s removable parts are dishwasher safe, whereas the Keurig K Duo’s parts need to be washed by hand. This makes the Hamilton Beach Flexbrew more convenient to clean than the Keurig.

Both machines are descaled in the same way. The only difference in the descaling process is that the Keurig will tell you when it needs to be descaled whereas with the Hamilton Beach Flexbrew you need to decide for yourself when descaling is required.

Since the frequency that you need to descale a coffee machine depends on the mineral content of water in your area, the Duo telling you when it needs to be descaled should increase its longevity over the Flexbrew.

The Keurig K Duo’s removable reservoir makes it easy to clean as you can take it to the sink to rinse it out. With the Hamilton Beach Flexbrew, you have to try and clean the reservoirs while it is in the machine which is more difficult.

I have found that my Keurig K Duo is messy to use. It often “sneezes” coffee on the drip tray and counter when brewing and it is impossible to pour from the carafe without it spilling water out of the side of the lid.

There are similar complaints about the Hamilton Beach Flexbrew online (here, for instance) so messiness seems to be an issue for both machines. I suspect that this is because both machines try to cut costs on build quality so leaky mechanisms are an issue.

Winner: Keurig K Duo

Overall Ease of Use Winner: Keurig K Duo

The Keurig K Duo’s well-thought-out control panel makes it easier to use than the Hamilton Beach Flexbrew. Both machines create a seemingly unnecessary amount of mess, however.

Quality of Coffee

The quality of coffee that both machines produce varies a lot depending on the type of coffee that you make. I am therefore going to split this section into the quality of:

  • 6-8 oz K cups
  • Single-serve coffees over 10 oz
  • Carafe servings of drip coffee

Quality of 6-8 oz K cups

Both machines brew K cups in the same way, with water entering the K cup in one hole at the top and exiting the cup in one hole at the bottom.

The key difference between these machines, as far as the quality of brewed K cups is concerned, is that the Keurig K Duo has the “strong” functionality for K cups.

The longer brewing times created by the “strong” functionality do significantly improve smaller K cups and means that the Keurig K Duo will produce a better small K cup coffee than the Hamilton Flexbrew

Winner: Keurig K Duo

Quality of Single Serve Coffees over 10 oz

Both machines can brew K cups over 10 oz. Only the Hamilton Beach Flexbrew can brew single serves (up to 14 oz) using loose coffee grounds. This means that the Hamilton Beach Flexbrew can create better single serves over 10 oz.

As I explained in detail in my review of the Keurig K Duo, K cups only hold enough coffee for 6 oz – 8 oz of water. This means that K-cup coffee in larger servings than this will be watery. Even the largest reusable K cups can only hold enough coffee for 10 oz servings.

The single-serve filter coffee port on the Hamilton Beach Flexbrew holds enough coffee to make a 14 oz coffee with a 15:1 coffee-to-water ratio. K cups get nowhere near to this at 12 oz (or even 10 oz) servings.

Therefore you are much better off with the Hamilton Beach Flexbrew if you are planning to use it for larger single-serve coffees.

Winner: Hamilton Beach Flexbrew

Quality of Drip Coffee

Both machines make fairly poor coffee with the carafe side. This is due to the fact that neither machine can heat the amount of water needed for these servings at a hot enough temperature.

Although the Hamilton Beach Flexbrew offers a “bold” setting that increases the brewing time on the carafe side (something the Keurig K Duo does not do) for coffees of this size a couple of extra minutes does not make much of a difference to coffee flavor if the water is not hot enough to start off with.

Therefore there is little in it between the quality of carafe coffee from these two machines.

Winner: Draw

Overall Quality of Coffee Winner: Hamilton Beach Flexbrew

Although the Keurig K Duo does make better small K cup servings than the Hamilton Beach Flexbrew, the Flexbrew makes better single serve overall due to the fact that you can use loose grounds and therefore achieve a much higher coffee-to-water ratio. The drip coffee from both machines is quite poor, unfortunately.

Durability and Known Issues

Both machines’ exteriors are largely made from cheap, thin plastic meaning that any hinges (such as those that operate the coffee port lids) are liable to break if used with force.

The Keurig K Duo is beset with technical issues, some of which I have experienced myself. Its most common technical issues are:

  • The machine brewing less coffee than you programme it too
  • The machine going into descale mode too often (and sometimes permanently)
  • The machine stopped working in under a year of use

The “descale mode” does seem like an unnecessary potential point of failure in the Keurig K Duo. The risk of the machine completely locking up just to accommodate a feature that reminds you when to descale it does not make sense. The Hamilton Beach Flexbrew has no such feature, and therefore no such point of failure.

I could not find complaints online of similar issues in the Hamilton Beach Flexbrew, however, because the machine is less popular, there was less discussion about it generally online.

I did, however, find multiple complaints about the machine leaking coffee and water from its bottom. There are multiple videos about how to fix this online (indicating that it is a common problem) and the fix looks tricky.

Overall Durability and Known Issues Winner: Hamilton Beach Flexbrew (although this could just be due to a sample bias as the Keurig K Duo is a more popular machine)

I’ve found the Keurig K Duo to be so poorly designed and unreliable that I couldn’t award this to the Hamilton Beach Flexbrew.


DimensionHamilton Beach FlexbrewKeurig K Duo
Height13.70 inches12.92 inches
Width12.20 inches10.94 inches
Depth11.40 inches12.76 inches
Lid up Height18.20 inches16.90 inches
Mug clearance
(drip tray removed)
5.00 inches
(8.00 inches)
6.25 inches
(7.25 inches)

The Keurig K Duo has a slightly larger footprint than the Hamilton Beach Flexbrew, however, this difference is so small I cannot see it affecting your ability to fit either machine on your counter.

The Flexbrew’s extra inch and a half in lid-up height over the Keurig K Duo may well make it a significantly more cumbersome machine to use, especially if you have low clearance between your kitchen counter and cabinets.

Overall Size Winner: Keurig K Duo

The Keurig K Duo benefits from having an inch and a half lower maximum height than the Hamilton Beach Flexbrew. This could be the difference between having enough cabinet clearance space to use a machine and not.

Overall Winner: Hamilton Beach Flexbrew

I’d recommend the Hamilton Beach Flexbrew over the Keurig K Duo mainly because the former coffee machine allows you to make single-serve coffees with ground coffee as well as K cups.

This vastly improves the quality of single-serve coffees that you can get from the Flexbrew compared to the Duo.

The Keurig K Duo does almost nothing to justify its extra cost compared to the Flexbrew. It seems that you are just paying for the brand name.

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