Keurig K40 vs K55

Keurig has long had a reputation for producing excellent single-cup coffee makers. Their products have for years many attracted a broad audience worldwide among those that appreciate the ease and convenience of the K-Cup brewing system and who like a variety of flavors that this system offers. The company provides a range of product sizes and configurations to meet every home coffee brewing need.

Keurig has introduced their newest coffee maker model, the K55 intended to replace the older K40 model. Both models carry on Keurig’s tradition of excellent single-cup machines, using the proven K-cup brewing system. Each produces a rich, smooth, and delicious cup every time with the quality you expect from Keurig.

What’s The Difference Between The K40 and K55?

These two units share many features in common. They are both single-cup brewing service and are engineered for quality and long life. They both deliver high-performance brewing utilizing the K-Cup system for consistency and convenience.

But there are several significant differences between the two units. We’ll discuss the K40 first, then the K55 a little later.

The Keurig K40

Of the two models presented here, Keurig’s K40 Elite Brewing System is the older and is no longer available directly from Keurig. (It is no longer listed on the Keurig website.) This could make some buyers, those who want the latest model or are concerned about ongoing product support, reluctant to purchase this unit.

As discussed above, the unit is straight forward and easy to use single-cup coffee maker, but it does lack some of the features found on Keurig’s new models.

The significant difference between the K40 and the K55 is that the K40 does not have internal water filters, leaving the brewer at the mercy of their water supply. Those who live in areas with hard water or other contaminants may be less than satisfied with their beverage. This issue could be of course avoided by the use of only bottled water when brewing, but this would result in increased expense and inconvenience.

Online reviews of the K40 were good, with the product receiving four stars on a five-star scale. Many users were positive, appreciating the ease of use and the ability to make a quick cup of coffee that this machine offers.

Some reviewers, however, stated that their units only lasted a short time (less than one year). Others reported that they missed the more sophisticated controls and features that newer models provide.

The most common negative report was that brewed coffee tasted of plastic and this off-taste took a long time after purchase to go away. This is most likely due to the K40’s lack of water filtering capabilities.

As a discontinued item, availability of the K40 is somewhat limited and decreasing. Many online retailers still carry some stock; however, choices could be less than on new models. For example, only carries this unit in the color black. Support for this older model will likely decrease faster that Keurig’s newer models.

The Keurig K55

The K55 is Keurig’s replacement for the older K40 model and will appeal to connoisseurs looking for the latest and greatest in single-sup coffee makers.

Unlike the K40, this model can be used with Keurig’s optional water filters for consistent flavor delivery, regardless of the original water quality. This allows the brewer to use the unit with confidence, not worrying about off the off tastes that can be an issue in hard water environments.

These filters fit in the water reservoir and install quickly. The cost of six filter cartridges (a one-year supply) is around $25, inexpensive when compared to the cost of bottled water if required.

The K55 also supports Keurig’s My K-Cup reusable coffee filters, allowing you to use your coffee or tea when brewing. This unit is dishwasher safe and compatible with any cup size offered by the K55.

Being a newer model, the K44 is available from a wide range of retailers, or directly from Keurig. The unit is available in a variety of colors to match any décor, including black, blue, white and red.

Reviews of the K55 are slightly better than those of the older model, earning 4.5 out of five stars. A large majority of reviews were very high (five stars), with only a few negative (one star) reviews. Of the negative reviews, reports of leaks or the unit simply not working were common. Loud brewing noises were also reported.

Which One Should I Buy?

There is, in fact very little to choose between these two Keurig models. Both serve the same function of a single-cup coffee maker. Both use the same technologies and the same K-Cup brewing system. Both have a similar user interface and the same water-holding capacity.

Our recommendation would be the K55. With its higher overall user rating and ability to support more accessories, particularly water filters, we feel that this product would be a better value. We also liked that the product was in production and fully supported by Keurig. As a bonus, the K55 comes readily available in a range of colors, easily fitting in with any home décor.

Either machine will do the job, but our best bet is the newer Keurig K55.

What’s The Same?

The K40 and K55 are similar, with the K40 being the older of the two models. First, let’s tell you about the same features they have and how they are operated and maintained. We’ll talk about the differences between the two coffee makers later on.

The K40 and K55 are single-cup coffee makers and share many of the same features. Both can brew the perfect cup of coffee in under one minute. Multiple serving sizes are available on both units, allowing you to brew 6, 8 or 10 oz. cups using Keurig’s patented K-Cup technology.

The K-Cups come in a variety of flavors, including coffee, decaffeinated coffee, and hot cocoa. Keurig recommends using the 6-oz. brew size to achieve the strongest brew.

With either coffee maker, you can also brew iced tea or get hot water simply by pressing down on the brew handle without a K-Cup placed in the unit.

Setup and operation

The initial setup on each machine is easy. Just remove the unit from its packaging, assemble a couple of components, such as the water reservoir and fill the reservoir with water.

Both the K40 and K55 models Keurig’s patented K-Cup technology for ease of brewing, consistent brewing strength and flavor, and easy, no-fuss cleanup.

The K-Cups come in a wide variety of flavors and are even offered by chain coffee stores, such as Starbucks and Dunkin’ Doughnuts. These extensive offerings allow you to explore new flavor sensations, as well as remembering your old favorites.

Brewing the perfect cup of coffee is easy with Keurig. Just insert a K-Cup into the pack holder, press down the brew handle, place a mug on the drip tray and press the brew size. The unit will quickly heat up, brewing the perfect cup of coffee in under a minute.

When the brewing cycle if finished, the machine will purge the system of water with a burst of air, keeping the device clean for the next perfect cup.

Capacities and controls

The 48-ounce water reservoir in both units allows you to brew up to six cups before refilling. The reservoir is removable on both the K40 and K55, allowing for easy, convenient filling whenever you need to. You have two choices to fill the reservoir; just remove the reservoir lid and fill with water, or remove the reservoir from the unit and fill. You can fill the reservoir with water the night before, simplifying and saving time in your morning routine.

The user controls are similar to both models, featuring programmable, easy to use push-button technology to activate product features. Controls allow you to turn the unit on or off, select brewing cup size, and enable or disable the auto-off feature

Viewing the status of both the K40 and K55 is easy through LED indicator lights. At a glance, you will know if the power to the unit is on, whether the unit is heating and the size of the serving cup selected.

Additional lights let you know when it is time to refill the water reservoir and when it is time to descale the machine (discussed below). Overall, Keurig has provided an easy, efficient user interface, letting you know the unit’s status at a glance, leaving little guesswork in brewing your perfect morning cup of coffee.

The auto-off feature of both machines is programmable and turns off the unit after it has been on for two hours, saving energy and money. This feature can be turned on or off by using the push button control and an indicator light lets you know if the feature is active.

The removable drip tray on both units allows for easy cleanup and accommodates travel-size mugs.

Style and size

Both units are smartly designed to fit in with kitchen or office decor. User controls are featured prominently at the top of the machine, on the right side for easy viewing. The clear water reservoir, allowing you to see the amount of remaining water easily, is on the left side. The brew handle, pack holder and drip tray are prominently featured at the front of the coffee maker.

The compact size of both the K40 and K45 is similar, making for easy to place on a kitchen countertop and under upper kitchen cabinets. Both units weigh under 20 lbs. making for easy moving and relocation, should the need arise.


Both units do require some maintenance to maintain peak performance. Keurig recommends that if their coffee makers have not been used on over a week, that water is purged from the internal tank.

Purging is a simple process that involves removing the water reservoir, then cleaning and refilling it with fresh water. From there, lift the brewing handle and then lower the handle without a K-Cup inserted in the pack holder. This will replace old water in the internal tank, replacing it with fresh, clean water from the reservoir.

Keurig does recommend descaling both the K40 and K55 periodically when the descaling light is illuminated. This is accomplished by filling the reservoir with vinegar and pressing the brew button without a K-cup in the pack holder, making sure that the auto off feature is disabled.

Place a large mug on the drip tray and press the brew button. This process is the repeated until the reservoir is empty and the add water light is illuminated. From there, leave the unit for four hours while still on. Then discard any remaining vinegar in the reservoir, rinse the reservoir thoroughly and refill with clean, fresh water.

Again, place a large mug on the drip tray and press the brew button without a K-cup in the pack holder. Repeat the process until the reservoir is emptied and the add water light is illuminated. If the descaling light remains illuminated, the process should be repeated.

Rinsing will remove any vinegar and scale from inside the unit, replacing it with clean, fresh water. Descaling when recommended will keep your brewer in top condition, ready for the next perfect cup.

Cleaning the K-Cup pack holder assembly is also a simple process. Just remove the pack holder from the machine by grasping it firmly and pulling towards you. Place the pack holder on the top rack of your dishwasher.

A low-temperature cycle should be used in your dishwasher. The pack holder can also be cleaned by hand, using mild dish detergent. Following these steps will keep the pack holder clean and fresh for its next use.

Other internal components, including the funnel and the exit needle, also require periodic cleaning. The funnel can be placed in the dishwasher, as noted above, and the procedure for maintenance of these items is located in Keurig’s product manual that ships with the unit.

Cleaning the exterior of both the K40 and K55 is quick and easy. Simply wipe down the coffee maker with a damp, soapy, non-abrasive cloth and rinse thoroughly. Keurig components should not be placed in the dishwasher except for the pack holder and funnel).


Keurig warrants both coffee makers for one year from the date of purchase to be free from defects in materials and workmanship under normal home use. They do recommend that you promptly return the product warranty registration card.

Keurig will replace or repair, at their option any unit found to be defective. However, you must use only Keurig Brewed K-Cup brand brewing packs and accessories. You can obtain warranty service by calling the manufacturer on their toll-free number, listed in the product manual.