Best Bottle Warmer
Best Overall Bottle Warmer
Tommee Tippee 3-in-1 Advanced
The Tommee Tippee 3-in-1 Advanced is a warmer that heats bottles using a water bath. We prefer this method as we think it is safer and more consistent than steam. The four-button interface is intuitive and straightforward to use and considers different variables, such as bottle type, milk temperature, and the volume of the contents. The inner chamber is large enough to fit most wide neck bottles, and the basket allows you to lift out shorter containers without risk of burned fingers. It earned the highest overall score in our testing and is a device we would gladly use in our own homes.
The large size of the 3-in-1 Advanced may not be ideal for those who have a small kitchen or would like to use it outside the home. The warm time of the Tommee Tippee is not as fast as some others, but we gladly accept a longer wait if it means getting a more consistent milk temperature. Overall, we love this Tommee Tippee product and highly recommend it as your primary warmer.
Read Review: Tommee Tippee 3-in-1 Advanced
Innovative Bottle Warmer
The Kiinde Kozii is an innovative warmer with outstanding performance. It earned the second-highest overall score in our tests, quickly becoming a tester favorite at home, on-the-go, and even at daycare. It has many notable qualities, including a simple, user-friendly design, accommodates all bottle shapes and materials, a handy quick start guide, a small footprint, an auto shut-off feature, and a retractable water reservoir. But, what we like best about the Kozii is the SAFEHeat technology that uses a warm, circulating water bath to heat bottle contents and reduce the risk of nutrient damage.
While not as speedy as steam heat technology nor as fast as much of the competition, even with these minor flaws, we think it is well worth the wait to take advantage of the other beneficial features.
Read Review: Kiinde Kozii
Best Bang for the Buck
The Chicco NaturalFit is a simple, straightforward warmer with a budget-friendly price. It is a safe, reliable way to heat your baby's bottle without the bells and whistles that make a product complicated or hard to use. This product uses water bath technology with a slow but consistent warmer. Its strengths lie in health and safety, ease of use, and cleaning. It is multifaceted, and compatible with a variety of bottle dimensions and materials, and has a small footprint and compact volume for easy and convenient travel.
This warmer is somewhat slow and could leave your little one fussy while you wait for a warm bottle. However, we believe the lower price and consistent warming temperature are significant and overshadow the downsides, making this wallet-friendly option an excellent choice for most families.
Read Review: Chicco NaturalFit
Best for Travel
Tommee Tippee Travel Warmer
The Tommee Tippee Travel Warmer is an innovative product made with on-the-go families in mind. The insulated flask stores warm water, and the extra-large beaker acts as a warming chamber that is big enough to hold most sizes of bottles, pouches, or baby food containers. To prep the warmer, all you need to do is boil water beforehand, and then all parts fit together in a self-contained unit that fits neatly in a diaper bag or stroller basket. A hot water bath brings milk to a temperature suitable for a baby without using an external warming source.
Unfortunately, due to the Travel Warmer's ultra-simplistic nature, it lacks safety features such as an auto-shutoff or end of cycle alarm. It also heats bottles slowly and somewhat inconsistently, as there is no circulation in the water unless you manually swirl the beaker. However, if you are looking for a convenient way to warm up your baby's food while away from home, the Tommee Tippee Travel is a potential contender.
Read Review: Tommee Tippee Travel Warmer
Why You Should Trust Us
At BabyGearLab, we provide readers with the world's most scientific reviews of baby gear. Leading our team since 2012 is founder Dr. Juliet Spurrier, a board-certified pediatrician and mother of two. Using her knowledge of all-things-baby and experience as a medical practitioner, Dr. Spurrier selects products with safety and efficacy in mind to develop the important metrics included in testing. Also contributing to this review is Senior Review Analyst and father of seven, Bob Wofford, as well as Senior Review Editor and mother of two, Wendy Schmitz, both testing and reviewing baby gear at BabyGearLab since 2013 and 2014, respectively.
Having researched more than 35 warmers, over time, we've tested more than 21 contenders side-by-side. We measure multiple factors such as warming temperatures, warming times, ease of use, safety, and ease of cleaning. Our extensive and detailed testing takes place over several months and in various settings, including in-house at BabyGearLab, in homes of testers, and at daycares. This iteration includes 11 impressive products.
Analysis and Test Results
While it isn't a necessity, some parents may find having a bottle warmer is a welcome addition to the baby gear arsenal. If you have multiple babies or are only bottle-feeding, a simple, convenient, and safe option for heating your baby's meals could be a big time saver or a stress reducer. Think of it as an extra set of hands!
However, not all warmers are equal, especially when it comes to ensuring that your precious breastmilk is not overheated. During our extensive testing, we focused on metrics such as health and safety, ease of use, warming efficiency, and ease of cleaning to find the best. All warmers were put through the wringer in comparative testing over several months, considering key operational features in day-to-day use. Our scores reveal both the performance of each warmer and the differences between each.
Luckily, if you find yourself in need of a warmer, most of them are reasonably inexpensive compared to other baby gear items. The award winners in this group range in price from $35 for the Chicco Natural Fit to $70 for the Kiinde Kozii. The top-ranked warmer, the Tommee Tippee 3-in-1 Advanced, is $43. If you aren't sure how often you will use one or even if you need one, but you want to have one on hand just in case, the Chicco is your best bet at a wallet-friendly $35. It is hard to go wrong with the Chicco. It earned a third-place rank and has a faster heat time than other award winners.
Health and Safety
Health and safety are the most crucial consideration for choosing a bottle warmer in our minds. Warming a bottle should not overheat the contents or cause hot-spots, and it should not alter the nutritional or immunologic value of breastmilk. The Best Practices for Handling Breast Milk, to uphold the nutrition, is to avoid exceeding a temperature of 104 F / 40 C and ideally, staying at or below body temperature, 98.6 F / 37 C.
Throughout testing of the warmers, we quickly came to prefer products with warm water bath technology over steam heat, mainly because they aren't as hot and have a reduced risk of a scalding injury to you and your baby. Bottles tend to come out of these warmers cooler and more comfortable to handle without a lower likelihood of overheating internal contents.
The Kiinde Kozii and the Tommee Tippee 3-in-1 Advanced each earned a satisfactory health and safety score. Both ranked among the highest of any products we tested, and both utilize water bath warming technologies.
Overheating Breastmilk Results in Nutrient Loss
The ideal drinking temperature for a baby's bottle is body temperature, 98.6 F / 37 C, or less. So, attention to temperature is essential, especially when it comes to breastmilk. As a living substance, breastmilk includes an incredible array of beneficial nutrients, like enzymes and probiotics, immune factors (such as IgG and IgM antibodies and immunoglobulin A), complex growth factors, and hormones.
However, 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 degradation rate. 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 breastmilk), 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 in health and safety, we did a comparative, controlled heating test to determine which options were more likely to heat to recommended temperatures and maintain breastmilk nutrients. We measured maximum temperatures at both manufacturer's recommended settings, in addition to fully cranking the maximum settings if a user doesn't follow recommendations. We also left the bottle in the warmer for up to 12 minutes to see how high temperatures will get if you forget the bottle is warming or can't get to it right away.
At recommended settings, we found that the Kiinde Kozii, Tommee Tippee 3-in-1 Advanced, and the Chicco NaturalFit all stayed below 104 degrees for the most extended amount of time while still reaching temperatures warm enough to keep your baby happy. Out of these three options, the Kiinde was also the fastest to reach proper warming temperatures without overheating. The Kiinde Kozii has the lowest temperature at shut-off, and the Tommee Tippee 3-in-1 Advanced is closest to body temperature at shut-off.
The Munchkin Speed earned the lowest score for health and safety in our tests. This unit is a steam product that can cause burns if the steam makes contact with your skin. Also, the Munchkin Speed overheated the bottle regularly if accidentally left in the warmer after shut-off. So while it heats quickly in about 2 minutes, if you are changing a diaper or soothing a crying infant, the bottle can overheat to temperatures up to 137 degrees in 5 minutes and 147 degrees at 12 minutes. Again, both alarming temperatures.
Overheating is Possible at Maximum Settings
A second test we performed was to set them to the maximum heating setting (not the manufacturer's recommended setting) to see if misuse of the warmer could result in overheating breastmilk.
Once again, we were impressed with the Chicco Natural Fit, which consistently heats to safe temperatures that are neither scalding nor degrade breastmilk. Its performance in our basic test and the maximum settings test show consistency and less chance of error.
The Kiinde claims that they rely on a patent-pending SAFEHeat technology to prevent milk from overheating using a circulating warm water bath. However, we were able to get it to overheat in our maximum heating test. When set at maximum heating, the Kiinde continued to heat, eventually reaching temperatures we consider to be overheating. After 8:30 minutes, it crossed 104 F. After 12 minutes the milk temperature rose to 122 F. We conclude that it is crucial to follow Kiinde's recommended settings for best results, and not rely on the manufacturer's claims.
The Munchkin Speed is the fastest and most likely option to overheat the bottle's contents. When used at maximum heating settings (not recommended), the steam heat warmer pushed temperatures up to a scalding 150 F. This is way too hot to warm anything baby will drink, which is a severe concern for us. Even though this test used settings outside of the manufacturer's recommendation, we suspect many parents could end up making this mistake for the sake of time or forgetting the bottle is in the warmer.
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 instructions can make it easier for you and other caregivers who may help you. We based our ease of use results on factors such as assembly out of the box, clear and specific instructions, quick set-up for each use, versatility, compatibility, portability, and useful elements like a water reservoir, timer, and auto shut-off.
The top-scoring warmers in the ease of use metric include the Tommee Tippee 3-in-1 Advanced and the Chicco NatrualFit, both simple and straightforward for set-up and use. They don't require a lot of prep or maintenance, and the user interface is intuitive and helpful.
A warmer with an integrated or attached water reservoir, like the Kiinde Kozii, Chicco NaturalFit, or Dr. Brown's Deluxe, can save you time and effort. You don't need to add water with every use. Steam-based warmers, like the Boon Orb, require you to fill a small vial with a precise amount of water each time you use the unit. It's easy to spend almost as much time filling the vial as you do waiting for the bottle to warm, which can get tedious.
Setting Timer and Warming Charts
Most products typically include charts to help you determine where to set the timer for perfect warming. These charts range from simplistic and straightforward to eye-crossing frustrating. Many of the instructions account for different bottle sizes and materials, as well as room temperature, refrigerated, or frozen milk, which can complicate matters.
We found that a bit of a fiddle factor is necessary to achieve the best results. Be aware that you will inevitably go through some trial and error before you consistently reach the perfect setting for daily use. However, it shouldn't take more than a day or so of fiddling to get a working mojo going with your new warmer. We appreciate that the timer settings of the Kiinde Kozii show in minutes. The Chicco NaturalFit also has simple controls with a dial turned to either baby food or bottle warming. The Tommee Tippee 3-in-1 Advanced has a few more settings, but the snowflake icons make it simple to understand.
A few steam-based warmers like the Munchkin Speed and the Boon Orb include a lift-out "basket" to aid in removing the bottle since it can become too hot to handle after a warming cycle.
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 it is compatible with your preferred bottle's width, height, and material. Dr. Brown's Natural Flow Glass baby bottles are narrow and tall, and fit well in a Dr. Brown's Deluxe warmer. However, don't expect this unit to accommodate a wide-mouth design bottle like the Tommee Tippee Glass feeding bottle or Comotomo. Some warmers are more versatile, which can be useful if you need to switch bottle types at any point or hope to warm breastmilk storage pouches.
Also, if using glass bottles, make sure the bottle warmer you choose is compatible with glass. For example, Boon Orb is a no-go as rapidly rising temperatures make glass prone to breakage in this unit.
If you are unsure of what bottle your baby will prefer, consider a versatile warmer like the Tommee Tippee 3-in-1 Advanced, Kiinde Kozii, or Chicco NaturalFit. These warmers function well with all bottle shapes and materials, including breastmilk storage pouches.
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 essential. The Chicco NaturalFit has a small overall footprint and doesn't have multiple parts that could get lost, so it is an excellent travel option. The Tommee Tippee Travel Warmer is explicitly made for this scenario, and is also a good option that does not require electricity. If you worry about height, shy away from the Baby Brezza Safe and Smart, the Beaba BabyMilk, and the Dr. Brown's Deluxe, which are all taller than 10.5 inches and could struggle to fit under upper cabinets.
Warming efficiency is a warmer's ability to consistently warm a bottle's contents quickly to a similar temperature each time. No cooling period or shorter wait time between heat cycles is also beneficial, especially if you have multiples or are operating 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 warm bottles quickly.
However, as mentioned earlier, steam heat has its drawbacks. For example, the Boon Orb's energetic steam heat technology is not compatible with glass bottles due to breakage potential during rapid temperature changes. Similarly, the steam heat of the Dr. Brown's Deluxe can overheat bottle contents. More importantly, both of these warmers present a real risk of overheating milk if used at their maximum settings.
With the water bath warmers, the warming process takes significantly longer. The Kiinde Kozii was 80F degrees at 5:30 minutes, and the Tommee Tippee 3-in-1 Advanced was almost 90F at 5:00 minutes. The Chicco NaturalFit took a little longer with 80F at around 8:30 minutes. We think these longer times are worth the wait so that the bottle contents aren't too hot, and the risk of steam related injury isn't a concern.
We recommend thawing frozen breastmilk overnight in the refrigerator before use. Thawing will shorten warming time, which means you'll be able to get that hungry baby drinking faster.
Consecutive Warming Cycle Wait-Time
Some warmers have recommended wait times between running consecutive warming cycles. Being able to start another warming cycle immediately is useful if two or more bottles are being heated back-to-back, such as with multiples or if the warmer is in frequent use at a daycare center. It's also handy if the first cycle doesn't get the milk warm enough, and you need to add more time. We found the longest wait time between warmings is around 30 minutes or when the warmer has thoroughly cooled. The Chicco NaturalFit is one of these warmers, which is a deal-breaker for some families. The Tommee Tippee 3-in-1 Advanced has no listed wait time, while the Kiinde Kozii only has instructions to decrease the subsequent bottle's warming time by 30 seconds if the warmer still feels warm.
Ease of Cleaning
Regular cleaning and maintenance are essential, and the frequency (every day, every use, etc.) depends on the unit. The external cleaning process typically involves a quick wipe with a dry cloth.
However, because warmers use water, mineral deposits can build up internally. These deposits mean you need to descale the units every few weeks, particularly in areas with hard water (unless you have a water softener).
The descaling or demineralization process removes calcium and lime deposits that can build up on surfaces inside the warming chamber and the heating element after prolonged contact with water. Soaking the bottle warmer's internal surfaces in a vinegar solution, explained in manufacturer instructions, will remove deposits. The Kiinde Kozii has special instructions to soak the unit with a mild 1:50 bleach/water solution every few weeks. In the case of the Chicco NaturalFit, some products require overnight soaking, which could be a deal-breaker if you rely on your warmer for every feeding.
In addition to these measures, we considered how difficult it is to get things very clean. Some products have hard to reach nooks and crannies—the Dr. Brown's Deluxe has a narrow and deep warming chamber and a poorly designed water reservoir that makes it impossible to get inside it for cleaning.
The units that scored well in this metric had fewer parts and accessories and easy-to-access water reservoirs. The Tommee Tippee Travel Warmer is simple to clean and does not require descaling. Another is the Boon Orb, while the rest of the units finished slightly lower with similar instructions and effort levels for sufficient descaling. Our least favorite to clean, and most likely to accumulate residue or mildew build-up even with regular cleaning, is the Dr. Brown's Deluxe.
In our process of repeatedly testing the most popular bottle warmers over the last eight years, we've learned a lot of information we'd like to share about essential qualities and features you'll want to look for when making a purchase.
Why Purchase a Bottle Warmer?
While not a necessity, if you're warming more than one or two bottles a day or your baby prefers milk to be a specific temperature, you may find it convenient to have a warmer.
The bottom line is that a bottle warmer can be a convenient time-saver, but it is not a must-have baby product. So, let's look at the alternatives side-by-side to help you assess whether the cost justifies the convenience.
Breastmilk starts degrading in nutritional and immunological value at 104 F / 40 C, but deterioration accelerates as temperatures climb higher than 113F/45C. You should aim to warm baby's milk to approximately 98.6 F / 37 C (body temperature) or less.
Three Ways to Warm a Baby Bottle
It's the middle of the night. Baby is hungry, and it's your turn to feed him. Time for the midnight shuffle. Do you grab the baby and then go warm the bottle or vice versa?
Good options for warming the bottle include:
- Stand at the sink while swirling the bottle under warm tap water (not too hot)
- Put the bottle into a bowl of warm water with intermittent swirling (again, not too hot)
- Use a bottle warmer
The first two options require constant attention, which is asking a lot when you're half asleep with a hungry, crying baby. The advantage of a dedicated warmer is that your hands are free, and you can focus on your baby's other needs like a diaper change or cuddle time.
Is it worth it? That's a personal decision, but many parents find the convenience worth the cost, especially if you plan to bottle feed or share night duties with your partner to catch up on some valuable sleep.
You should never use the microwave to heat your baby's meal, not for formula, breastmilk, or purees. High, focused heat generated by a microwave, can result in dangerous "hot-spots" in liquids and solids. If not correctly mixed, cooled, and checked, this can result in scalding injury to the baby. Also, a microwave is likely to heat at least some, if not all, of the breast milk above 104 F / 40 C, the temperature at which beneficial enzymes, nutrients, and antibodies begin to degrade, reducing healthful benefits for the baby.Furthermore, putting a bottle in a pan of boiling water or just boiled water can also lead to overheating and should not be done.
Selecting the Right Product
Apart from the convenience of being hands-free when warming a bottle, a great bottle warmer should deliver on the following five factors:
- Health & Safety — Avoiding the risk of burn injury and provide nutritionally whole breast milk at an appropriate temperature for the baby is essential. Generally, a good rule of thumb is to heat to near body temperature 98.5F/37C and not much higher—more on this below where we discuss how to preserve the full nutritional value of breast milk.
- Efficiency — Ability to warm contents quickly and consistently
- Ease of Use — Easy to operate and maintain
- Versatility — Accepts different shaped bottles of any material
- Portability and Footprint — Easy to transport and fits in your kitchen
Preserve the Full Nutritional Value of Breast Milk
As we describe in our breastmilk advice, your breastmilk is "liquid gold" in its nutritional value for your baby, but the nutrition can be degraded by overheating.
Once you warm breast milk to temperatures higher than 104 F / 40 C, its nutritional and immunological value begins to deteriorate, both of which are crucial to a baby's health and immunity. However, degradation does not become severe until temperatures rise above 113F / 45C. For example, in a study conducted by the University of Manchester, breastmilk heated for 10 minutes at 113 F / 45 C showed a 10% loss of essential nutritional activated enzymes. And, just 1 minute at 131 F / 55 C results in a 50% loss of activated enzymes, but no significant damage occurred after 20 minutes at 104 F / 40 C (or lower temps).
Luke Warm, Not Hot
Keep in mind that the ideal breast milk temperature is around body temperature, 98.6 F / 37 C, or less, which feels lukewarm.
Options and Features
Bottle warmers come in all shapes and sizes and use two different methods to warm your baby's meal.
Water Bath Versus Steam Heat Technology
Bottle warmers use either a warm water bath or steam heat while a few have both.
A water bath warms breastmilk or formula gently by circulating warm water around the bottle. They tend to heat slower but more consistently without the high temperatures required to produce steam. We recommend a bottle warmer that uses water bath technology. The benefits are this gentle warming helps breastmilk retain maximal nutrients, maternal antibodies, and other potential health-promoting factors. We also consider it safer as the water used is warm rather than hot, potentially scalding steam.
Of the bottle warmers we tested, the Kiinde Kozii, Tommee Tippee 3-in-1 Advanced, Chicco NaturalFit, the Baby Brezza Safe and Smart, and the Philips AVENT Fast are water bath warmers.
With steam heat, water inside a reservoir comes into contact with an internal heating element (like a hot plate), which produces steam that heats liquid bottle contents. While this method usually heats faster than water baths, hot water and scalding steam rise to very high temperatures. The result? The bottle's exterior is often wicked hot after a heat cycle, typically necessitating a cool down before being useful. If spillage of warmer contents were to occur, the risk of burn injury is present. Also, steam does not always heat evenly. This uneven heating means that significant temperature variations may exist throughout the contents of a heated bottle, and without thorough mixing and checking, hot-spots are a risk. In our opinion, these high temperatures carry unnecessary risks.
Lastly, because steam heat typically generates high temperatures, there is increased potential for nutritional degradation of breastmilk if brought to temperatures >104F/40C. We found in our testing that a few of the units make it much too easy to overheat breastmilk, which results in a significant loss of nutritional quality. The warmers in our review with steam heat technology are the Munchkin Speed, Dr. Brown's Deluxe, Beaba BabyMilk, Baby Brezza Safe and Smart, and the Boon Orb.
Baby bottles can be narrow or wide and short or tall. As such, some containers may not fit inside the bottle warmer's chamber. Also, material limitations may mean that a certain warmer isn't compatible with a particular baby bottle like the Boon Orb and glass bottles. Also, some bottle warmers (usually steam technology) require either plastic or shatter-resistant glass like borosilicate found in Lifefactory Glass Bottle because the quick heating process may cause the glass to break.
If you are uncertain which bottle type and nipple your baby prefers (i.e., they haven't been born yet), choosing a bottle warmer that accommodates all bottle sizes and materials is smart. The Kiinde Kozii and the Tommee Tippee 3-in-1 Advanced are excellent versatile choices and fit every bottle and pouch we tried. The Chicco NaturalFit is suitable for different bottle types but is not compatible with breastmilk storage pouches.
Auto Shut-Off Feature with Timer
We highly recommend buying a bottle warmer with an automatic shut off feature. Most warmers shut off automatically based on either a timer or a temperature reading. In our testing, the timer-based auto shut-offs were reliable and easy to use and read. Timers allow for some adjusting, and once you've found the time setting that's best for your baby, it's easy to remember for next use. Plus, it's helpful to know how much longer you'll need to wait before the bottle is ready for your baby. The only warmer in our review that does not include this feature is the Philips Avent Fast.
Though a temperature-based shut-off sounds ideal, we found that this method didn't work as well in practice, often under-heating bottles with a few overheating incidents. The one exception is the Chicco NaturalFit, which heat consistently to an adequate temperature without going over 100F/37.8C.
Audible End Beep
An audible beep at auto shut-off is useful because it is easy to get sidetracked with the baby when the bottle is warming. For many of the warmers in our tests, the milk's temperature will continue to rise if left in the warmer after the auto shut-off, which can lead to overheating. Because breastmilk begins to degrade significantly above at 113F/40C to 45C, removing a bottle promptly after the beep is essential.
Some warmers require that you add water each time, while others have a built-in reservoir that monitors the water for you and lasts through several cycles. The Kiinde Kozii, Chicco NaturalFit, and Dr. Brown's Deluxe do not require a refill with every use, which can save you valuable time and effort or at least late-night frustration.
Making Your Selection
Taking into account the various features and options and asking yourself the following questions can help you narrow down your options to help you find the best warmer for your family.
Consider Warming Efficiency
Since a bottle warmer's primary purpose is to provide your baby with a comfortably warm meal, this should be a high priority. You'll want to be able to toss in a bottle, tend to the baby, and return to a perfect meal every time. Some warmers can produce a consistently warmed bottle every time, while other warmer's results vary, leaving us with an overly hot or still cold bottle. Because time is precious, we urge you to consider a consistent warmer like the Chicco NaturalFit, which heats reliably close to the ideal temperature of 98 degrees each time. The Kiinde Kozi also warms consistently but has a lower final temperature.
Is It Easy to Use?
Before a bottle warmer can fit seamlessly into your routine, you have to learn how to use it. Out of the box, the warmers in our tests include a wide variety of "parts," ranging from one solid unit like the Kiinde Kozii to a machine plus many extra pieces. Other things to consider are the setting options and heating charts and how hard they are to remember or use. No matter what, using the warmer takes some adjustments and fiddling, but it should be close to the instructions.
It's essential to be aware that you will inevitably go through some trial and error before you consistently reach the perfect setting for the particular bottle and starting milk temperature that your baby uses most often. But it shouldn't take more than a day or so of fiddling to get your machine working correctly. Some of the easiest to use warmers are the Kiinde Kozii, the Tommee Tippee 3-in-1 Advanced, and the Chicco NaturalFit.
What's Your Bottle Style?
You'll also want to think about the type of bottle you'll be using. As we mentioned above, some warmers don't fit extra-wide based bottles like a Tommee Tippee. Other bottle warmers, like the Boon Orb, offer adapters for wide-mouth and narrow-mouth bottles. We find that the Kiinde Kozii, Tommee Tippee 3-in-1 Advanced, and the Chicco NaturalFit work the well with all bottle types, and the first two also work with milk storage bags.
Do You Have Multiples?
Lastly, you'll want to be aware that many warmers have a recommended wait time between running warming cycles consecutively. Being able to start another warming cycle immediately would be vital if you were heating two or more bottles in a row, say for twins. It's also handy if the first cycle doesn't quite get the milk warm enough, and you need to add more time. The longest wait time we found between uses was close to 30 minutes (or until the unit cools down) for the Chicco NaturalFit, while the Tommee Tippee doesn't list a wait time.
Can You Keep it Clean?
This metric is pretty self-explanatory, but something you'll want to consider. Although cleaning isn't always a per-use or even daily requirement, cleaning is essential to keeping this type of product in proper running order. We found that unless you spill milk on the unit, cleaning comes down to proper maintenance. Since this type of product uses water in some form or another to warm the bottle, the issue lies in mineral deposits forming somewhere on the unit, usually in the warming chamber and on the heating element.
Every warmer we tested instructs you to use a vinegar solution rinse on occasion (also called descaling) to get rid of these deposits (the Kiinde recommends a bleach/water solution). We also found that the warmers that use a reservoir system carry a higher risk for mold or mildew build-up in the reservoir itself, so they should be cleaned out more often to avoid that possibility.
Our main goal for testing bottle warmers is to assess the safety and see if each could warm a bottle of milk consistently and efficiently without overheating or damaging the contents' nutritional value. We also looked for ease of use and cleaning. We tested each warmer over several months to find the best products on the market.
Health and Safety
We performed two different controlled tests of each warmer using the same protocol; that is, we filled 4 ounces of refrigerated milk in a 4 ounce Lifefactory Glass Bottle with silicone sleeve. Each test started with milk between 42 F / 5.6 C to 45 F / 7.2 C. A professional-grade digital thermometer was placed directly in the center of the bottle to record temperatures.
An issue we found is the tendency of bottles to continue heating if left in the unit after shut-down. So, we kept the bottle inside the unit and continued measuring temperatures every 30 seconds for a full 12 minutes.
Please note — In our tests, we used a glass bottle with a silicone sleeve, which takes longer to conduct heat than glass alone or plastic. So, our milk temperature measurements are likely to be lower than if you use a plastic bottle. However, the times are still critical as they indicate which warmers heat faster than others.
Manufacturer Warming Recommendations
Following the manufacturer's recommendations, we tested the bottle contents for each warmer every 30 seconds. We also noted the milk's temperature when the unit turned off.
Maximum Heat Settings
We also tested each warmer by cranking a thoroughly cooled warmer to its maximum settings and let it do its thing with the same set up of 4 ounces of refrigerated milk in a small Lifefactory glass bottle with the included sleeve. We recorded temperatures every 30 seconds for a maximum of 12 minutes.Why did we do this?
We don't condone stepping outside the manufacturer's instructions, but let's face it, not everyone is going to play by the rules. We suspect some parents will try to find the fastest way to heat the bottle. So, in this event, we wanted to see how high the temperatures ascended with each warmer at full-throttle.
Ease of Use
For ease of use, we considered how simple it is to set up out of the box, the number of pieces, ease of day-to-day use, and the quality of instructions. We carefully read the directions, reviewed the initial assembly, and then took notes on how easy it was to use daily, over several months considering the warming chart, its location, adding water, and whether a caregiver could use the unit without significant coaching.
For warming efficiency, we took into account three factors. In our testing, we used body temperature as a standard to which to warm a bottle of milk. Reason? because that is roughly the temperature of breastmilk coming from the breast, and we assume this is the ideal temperature for feeding a baby.
Manufacturer Recommendations: Auto Shut-Off Time & Temperature
Following each manufacturer's warming recommendations, we recorded the time and temperature at auto shut-off.
Consecutive Warming Wait Time
Last, we considered whether a warmer could be used in tandem, as in warm one bottle, then put another right in to warm. Knowledge of waiting time is essential for those with multiples or in daycare scenarios.
Ease of Cleaning
Each recommends a simple wipe-down cleaning at least every other day. They all require occasional descaling for removal of hard mineral deposits to keep in good working order.
While a bottle warmer may not be vital for everyday life, it can provide an element of simplicity and efficiency, which may be worth it for many busy parents, especially those with multiples. To help you with your decision, we tested these warmers until we could confidently declare the winners.
— Juliet Spurrier, MD and Wendy Schmitz