The Best Bottle Warmer Review
What's the best bottle warmer for you and your baby? To find out, we put seven of the most popular and well-regarded bottle warmers to the test over a three month period, comparing them side-by-side during daily use. As part of our testing process, we used a digital thermometer to carefully measure warming temperatures to make sure that your precious breast milk is never over-warmed to the point that valuable nutrients are lost. We measured warming times, how convenient they were to use on a day-to-day (or night after night) basis, and other factors like ease of cleaning. Even with warmers that used similar technologies, our experiences produced surprising results; some good, and some, well, left us feeling a little chilled.
Read the full review below >
Test Results and Ratings
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Analysis and Award Winners
A number of useful qualities make it our favorite such as its simple, user-friendly design, compatibility with all bottle shapes and materials, a handy quick start guide, small footprint, auto-shut off feature, and a retractable water reservoir. However, what we like best about the Kozii is the SAFEHeat technology which uses a warm, circulating water bath to heat bottle contents and protect breast milk nutrients. While typically not as quick as steam heat technology, we think that it is well-worth the wait.
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Analysis and Test Results
Do I really need a bottle warmer? It's a question many new parents are faced with, and a good one at that. The reality is that although this type of product isn't a necessity, we found that if you choose the right one, it will quickly become a welcome addition to your baby gear arsenal. The best warmers provide a simple, convenient, and more importantly, safe option when it comes to heating your baby's meal, especially when compared to warming it in a bowl of hot water or running it under the tap. And as we'll discuss below, a warmer is far superior to microwave heating, a method that should never be utilized.
Some of the most common heating methods are to either stand at the sink while running the bottle under warm tap water, or to plunk it into a bowl or pan of previously boiled hot water. These are both mundane and require your full attention; not so easy when you have a crying baby at hand. However, thanks to technology, there's another option: enter the Bottle Warmer. Simply press a button on a specially designed machine, and voila! A hot and ready meal for your baby in minutes.
Good To Know: It's important that you never use the microwave to heat baby's milk. The high heat of a microwave can not only cause dangerous "hot-spots" but when it comes to breast milk, overheating also results in a deterioration of nutrients and other beneficial qualities important for baby's health and immunity.
Criteria for Evaluation
We found that not all bottle warmers are created equal. Most especially when it comes to assuring that your precious breast milk is not overheated to the point that nutritional damage occurs. In the following, you'll see how seven top bottle warmers performed when put to a detailed test.
We focused our testing on the following four rating metrics to find the best warmer:
All warmers were put through the ringer in comparative testing over several months, taking into account key operational features in day to day use. Our scores seek to reveal both the performance of each warmer as well as the relative differences between each.
Health and Safety
Best Practices for Handling Breast Milk, to uphold the nutritional qualities found in breast milk, it is best not exceed a temperature of 104 F / 40 C and ideally, should be at or below body temperature, 98.6 F / 37 C.
In our repeated testing and use of the 7 warmers in this round-up, we quickly came to prefer those products using warm water bath technology over steam heat simply because it isn't as hot and there is less risk of scalding injury. Bottles tend to come out of these warmers easier to handle on the exterior without as much likelihood to overheat internal contents.
Our two favorite bottle warmers, the Kiinde Kozii, which earned an 8 of 10 score in health and safety, and the Chicco NaturalFit which earned a 9 of 10 score, the highest of any bottle warmer we tested, are both based on water bath warming technologies.
Overheating Breast Milk Results in Nutrient Loss
The ideal drinking temperature for baby's bottle is body temperature, 98.6 F / 37 C, or less. However, attention to temperature is also important for breast milk itself as it contains a phenomenal array of beneficial factors including biologically active nutrients such as enzymes and probiotics, immune factors (such as IgG and IgM antibodies and immunoglobulin A), complex growth factors, and hormones.
An excellent study conducted at St. Mary's Hospital in the UK showed that no significant nutritional loss occurred in tests of breast milk heated to 104 F / 40 C for 20 minutes.
But, as temperatures rise over 104 F / 40 C, a degradation of nutritional and immunological benefits begins. In fact, scientific studies show that both temperature and duration at high temperature is very significant. Relatively little loss of nutritional value occurs until temperatures rise above 113 F / 45 C, but the higher the temperature, the faster the rate of degradation. For example, after 10 minutes at 113 F / 45 C, a study showed a loss of only about 10% of key nutritional activated enzymes. But, if you raise the temperate higher, to the temperature of hot tap water in many homes (too hot for breast milk), just a minute at 131 F / 55 C resulted in the loss of half the activated enzymes.
Basic Bottle Warming Test
To help differentiate warmers amongst each other in heath and safety, we did a comparative, controlled heating test to determine which ones were more likely to heat to recommended temperatures and maintain breast milk nutrients. Whether by water bath or steam heat, we measured maximum temperatures at both manufacturer recommended settings as well at fully cranked maximum settings in the event of a user not following recommendations. We also left the bottle in the warmer for up to 12 minutes to see just how high temperatures could get in the event a user forgot that a bottle was warming.
The graph below shows the results of that test.
What we found was that only two bottles performed ideally in this basic warming test. The Kiinde Kozii and the Chicco NaturalFit (the orange and green lines respectively in the graph above) both were unique in shutting off at about 80F and never overheating. The Kiinde was also the fastest to reach proper warming temperatures without overheating.
Two warmers, the Born Free Tru-temp and the Cuisinart BW-10, lost points in this test because they both shut off prematurely, and never reached target temperatures.
The Boon Orb earned the lowest score on health and safety based on our tests, with a 2 of 10. While it turned off at a proper temperature, it has no audible beep to alert the user and it continued to heat and then overheat the milk bottle if not removed. If left in the unit for just 1.5 more minutes, temperature rose to above 120 F. In fact, the Boon exhibited the fastest heat gain of any warmer in this review of between 6.7 to 8.4 degrees F/minute after auto shut-down. We find it disturbing that a warmer without an audible end beep, would have such a propensity to overheat. It would be difficult to tell that this unit has shut off unless a separate timer is set.
Overheating is Possible at Maximum Settings
A second stress test we subjected all the warmers to, was to set them to the Maximum heating setting (not the manufacturer's recommended setting), and see if mis-use of the warmer could result in overheating breast milk. Happily, 3 of the warmers never overheated, even when we tried to crank the heat up.
We were again impressed with the Best Value Award winner, the Chicco NaturalFit Two-in-One, which consistently heated to safe temperatures that neither were scalding nor to the point of degrading breastmilk. Its performance in our basic test, as well as the maximum settings test, gives us confidence in the product.
Two warmers which performed poorly in our basic warming test, had redeeming performances in the maximum heating test. Both the Born Free Tru-temp and the Cuisinart BW-10 appear to have excellent maximum temperature control, since even when used at maximum heating, both peaked nicely at approximately body temperature.
When used at maximum heating settings (not recommended), the Dr. Brown's Deluxe steam heat bottle warmer pushed temperatures up to a scalding 166 F / 74.4 C while the Philips AVENT Fast warmed up to a maximum of 138 F / 59 C using water bath technology. This is just too darn hot to safely warm anything baby will drink whether it be breast milk or formula and as such, and this is of concern to us, even though this test used settings outside of the manufacturer's recommendation.
Always swirl a warmed bottle for about 30 seconds to remove any potential hotspots and then check warmth of the contents by putting a few drops on your inner wrist to ensure correct temperature. The skin on your inner wrist is thin and sensitive to temperature. Milk warmed to body temperature will feel just a little warm, not too warm or hot.
Ease of Use
If your baby is exclusively bottle feeding, you may find yourself using a warmer every 2 or 3 hours. Having a simple, easy to use warmer with clear, reproducible instructions can make it easier for you and other caregivers who may help from time to time. Ease of use comprises 30% of the overall score in this review. We based it on factors such as easy to assembly out of the box, clear and specific instructions, quick set-up for each use, versatility, compatibility, portability and helpful elements like a water reservoir, timer, and compact design.
The top scoring warmer in ease of use with a 9 of 10 is the Editors' Choice Kiinde Kozii which out of the box is one solid unit. It is a simple warmer that doesn't require a lot of prep or maintenance and includes a "Simple Start Guide" which is helpful for babysitters. In contrast, the Cuisinart BW-10 was much more difficult to set up and use, and comes with a bunch of extra pieces in addition to the warming unit which requires some learning curve to master.
Having a warmer that either an integrated or attached water reservoir like with the Kiinde Kozii, Chicco NaturalFit, Dr. Brown's Deluxe, and the BornFree Tru-Temp makes a big difference as water does not need to be placed into the unit with each and every use as does with the Cuisinart BW-10 and the Boon Orb. These steam based warmers require you to fill a small vial with a precise amount of water for each use and it's easy to spend just as much time filling the vial or tube as you do waiting for the bottle to warm. This gets to be really tedious.
Setting Timer and Warming Charts
Bottle warmers typically include charts to aid in determining where to set the timer for the appropriate length of warming. These charts range from simplistic and straight-forward to virtually eye-crossing when sleep deprived. Many of the instructions account for different bottle sizes and materials, as well as room temperature, refrigerated, or frozen milk.
However, what we found after having navigated each warmer's manual was that no matter what, a bit of fiddle factor is likely needed be. Be aware that you will inevitably go through some trial and error before you consistently reach the perfect setting for daily use. Nonetheless, it shouldn't take more than a day or so of fiddling to get a good working mojo going with your bottle warmer. The timer settings of the Kiinde Kozii are based in minutes which intuitively makes sense. The Chicco also has very simple controls with just one setting for baby food and one for bottles. It has a temperature-based auto shut-off designed to turn off when the water heating the bottle reaches a certain temperature.
A few steam-based warmers like the Cuisinart BW-10 and the Boon Orb include a "basket" for removing the bottle or jar of baby food in case as these can become too hot to handle once a warming cycle is completed.
Compatibility and Versatility
If your baby is attached to a particular bottle and you are shopping for a bottle warmer, you will need to be sure that it is compatible with bottle width, height, and material as warmers. Dr. Brown's Natural Flow Glass baby bottles are narrow and tall and fit great in a Dr. Brown's Deluxe warmer. However, don't expect it to fit a wide-mouth design bottle like Best Value Tommee Tippee Feeding or Top Pick Comotomo. However, some warmers like the Cuisinart BW-10 and Boon Orb offer adapters for both wide-mouth and narrow bottles.
In addition, if using glass bottles, make sure the bottle warmer you choose is compatible with glass. For example, Boon Orb is a no go as fast rising temperatures make glass prone to breakage in this unit.
If you are unsure of what bottle your baby will prefer, go for a versatile warmer like the Kiinde Kozii or the Chicco NaturalFit Two-in-One which function well with all bottle shapes and materials.
Portability and Footprint
If you want to travel with a bottle warmer, have limited kitchen counter real estate, or want to fit your warmer inside a height-restricted area, a compact warmer is important. The smallest overall footprint goes to the Chicco NaturalFit Two-in-One with a small surface area of 33" and a height of 6", so this is a great option for travel. On the opposite extreme, the Born Free Tru-Temp when paired with its cooler takes up a mammoth 244" of surface area with a height of 9.5". Lastly, if height is a concern, shy away from the Dr. Brown's Deluxe; at 10.5" high, it is built to accommodate the characteristically tall and narrow Dr. Brown's baby bottles, like the Dr. Brown's Natural Flow Glass.
Warming efficiency is weighted at 25% of the overall score. For a warmer to receive a high score here, it needed to consistently warm a bottle's contents quickly and did not need a cooling period in between warming cycles such as may be encountered with multiples or in a daycare setting.
The fastest warmers in our tests are the Dr. Brown's Deluxe and the Boon Orb. Not surprisingly, these particular warmers utilize steam heat technology which helps them heat quickly.
However, as mentioned steam heat has its drawbacks. For example, the Boon Orb's energetic steam heat technology does not recommend that glass bottles be used due to potential for breakage during rapid temperature changes. Similarly, the steam heat of the Dr. Brown's Deluxe can overheat bottle contents. More importantly, both these warmers present a real risk of overheating milk if used at their maximum settings.
With the water bath warmers, the warming process does take significantly longer, from 5:50 to shut-off at 80F with the Kiinde Kozii and about 8 minutes with the Chicco. However these longer times are worth it, in our opinion, due to these two warmers being much less likely to overheat milk.
We recommend thawing frozen breast milk overnight in the refrigerator prior to use. Thawing will shorten warming time, which means you'll be able to get that hungry baby drinking quicker.
Consecutive Warming Cycle Wait Time
Two of the warmers have a recommended wait time between running consecutive warming cycles. Being able to start another warming cycle immediately is very important if two or more bottles are being heated back-to-back as with multiples or if the warmer is in use at a busy daycare facility. It's also handy if the first cycle doesn't quite get the milk warm enough and you need to add just a bit more time. The longest wait time for a bottle warmer in this review is with the Best Value Chicco NaturalFit Two-in-One with a recommended 15 minutes in between uses, or until the unit cools down. This could be a deal breaker for some.
The warmers without a wait time are the Kiinde Kozii, Dr. Brown's Deluxe, Philips AVENT Fast, Cuisinart BW-10, and the Boon Orb. The Dr. Brown's has a nifty functionality where if it is turned back on within 15 minutes, it executes a pro-rated reduction in its heating cycle. And, If the Kiinde system is warm, a reduction of heating time by 30 seconds is recommended.
Ease of Cleaning
Regular cleaning and maintenance of bottle warmers is important and the frequency (every day, every use, etc.) depends upon the unit. The external cleaning process typically involves a quick wipe with warm soapy or plain water.
In addition, because water is used inside warmers, mineral deposits tend to build up internally and they need to be de-scaled every few weeks to months, particularly so in geographic areas with hard water (unless you have a water softener in your home).
The de-scaling, or de-mineralization, process removes calcium and lime deposits which tend to build up on metal surfaces inside the warming chamber and/or on the heating element after prolonged contact with hot water. These deposits can be removed by soaking the internals of the warmer in a vinegar solution, according to manufacturer instructions.
The Kiinde Kozii recommends soaking the unit with a 1:50 bleach:water solution every few weeks. In addition to these measures, we scrutinized these warmers for how difficult it was to get things really clean, that is, hard to reach nooks and crannies as with the Dr. Brown's Deluxe (below left) with a narrow deep warming chamber and poorly designed water reservoir that makes it impossible to get inside for cleaning. The easiest to clean were the Chicco NaturalFit (below right) and the Boon Orb with a wide and shallow warming chambers and no water reservoir.
How to Choose the Best Bottle Warmer for more information.
— Juliet Spurrier, MD and Ruth and Ben Traxler
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