In our Bottle Warmer Review, we put seven of the most popular bottle warmers to the test and rated them on qualities such as health and safety, warming efficiency, ease of use and ease of cleaning. Through this testing, we distilled down important qualities you will want in any bottle warmer; the Editors' Choice Kiinde Kozii and Best Value Chicco NaturalFit are the cream of the crop. This buying advice guide explains it all in further detail.
Why Purchase a Bottle Warmer?
While a bottle warmer is by no means a necessity, if you're warming more than one or two bottles a day or your baby prefers for milk to be just the right temperature, then you may find it convenient to have one that is designed to safely, easily and consistently heat a bottle.
The bottom line is that a bottle warmer is a convenient time-saver, but it is not a must-have baby product. So, lets start by looking at the alternatives side-by-side to help you assess whether the cost justifies the convenience of a bottle warmer.
Breast milk 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 are half asleep with a hungry crying baby. The advantage of a bottle warmer is that your hands are free and you can focus on baby's additional needs like a diaper change or sweet cuddle time.
Is it worth it? That's a personal decision, but many parents find the convenience to be worth the cost.
Never use the microwave to heat baby's meal, whether it be formula, breast milk, or purees. High, focused heat generated by a microwave can results in dangerous "hot-spots" in both liquids and solids. If not properly mixed, cooled, and checked, this can result in scalding injury to baby. In addition, a microwave is likely 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 baby.Furthermore, do not put a bottle in a pan of boiling or even just boiled water (even if the stove top is off), as this is likely to result in overheating too.
Selecting the Right Product
Apart from convenience of being hands-free when warming the bottle, a great bottle warmer should deliver on the following five factors:
- Efficiency — Ability to warm breastmilk or formula quickly and consistently
- Ease of Use — Easy to operate and maintain
- Versatility — Accepts narrow or wide-mouth bottles of any material
- Portability and Footprint — Taking warmer on the go and use of counter space
Preserve the Full Nutritional Value of Breast Milk
As we describe in more detail in our related article, Best Practices for Handling Breast Milk, your breast milk is "liquid gold" in terms of its nutritional value to your baby. Yet, that nutritional value can be degraded by overheating.
Once breast milk is warmed to temperatures higher than 104 F / 40 C, its nutritional and immunological value begins to deteriorate, both of which are crucial to baby's health and immunity. However, degradation does not become severe until temperatures rise above 113F / 45C. For example, after 10 minutes at 113 F / 45 C, a study conducted by University of Manchester, UK breast milk showed a loss of 10% of key nutritional activated enzymes. But, even just 1 minute at 131 F / 55 C resulted in a 50% loss of activated enzymes. Yet no significant loss occurred after 20 minutes at 104 F / 40 C (or lower temps).
Luke Warm, Not Hot
Keep in mind that the ideal target for breast milk temperature is about body temperature or less, 98.6 F / 37 C, and less is fine. This is not very hot at all, really just luke warm.
Options and Features
Bottle warmers come in all shapes and sizes and use different methods to actually warm your baby's meal. Outlined below are key features to look for when selecting a bottle warmer.
Water Bath Versus Steam Heat Technology
Bottle warmers use water in one form or another to heat a bottle. Some warmers use a warm water bath while others use steam heat.
Of the bottle warmers we tested, the Editors' Choice Kiinde Kozii, the Best Value Chicco NaturalFit Two-in-One, and the Philips AVENT Fast employ use of a water bath in their warming process.
Dr. Brown's Deluxe, Born Free Tru-Temp, Cuisinart BW-10, and the Boon Orb, .
While usually heating faster than water baths, hot water and scalding steam rise up to very high temperatures. The result? A bottle's exterior is usually very hot upon finishing a heating cycle, typically necessitating a cool down prior to being held. In our opinion, these high temperatures carry unnecessary risk. If spillage of warmer contents were to occur, risk of burn injury is present. In addition, steam does not always heat evenly. This 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.
Lastly, because steam heat typically generates such high temperatures, there is increased potential for nutritional degradation of breastmilk if brought to temperatures >104F/40C. What we found in our warmer testing is that a few of the units we tested make it far too easy to overheat breast milk, which results in a significant loss of nutritional quality.
In addition, some bottle warmers require either plastic or shatter-resistant glass like borosilicate found in Lifefactory because the quick heating process may cause the glass to break. For example, the Boon Orb should not be used with glass bottles…period.
Because it is uncertain which bottle type and nipple your baby will prefer, choosing a bottle warmer that will accommodate all bottle sizes and materials is important. Both the Kiinde Kozii and the Chicco NaturalFit Two-in-One are great choices for versatility and fit every bottle, tall or wide, that we tried.
Auto Shut-Off Feature with Timer
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. And, it's helpful to know how much longer you'll need to wait. Timers allows 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. The Dr. Brown's Deluxe and Born Free Tru-Temp even have a memory for the previous setting.
Though a temperature-based shut-off sounds ideal, we found that this method didn't work as well in practice often overheating or under-heating bottles. The one exception is the Chicco NaturalFit Two-in-One which with its temperature-based system heated consistently to a good temperature without going over 100F/37.8C.
Audible End Beep
An audible beep at auto shut-off is important because it is easy to get side tracked with baby while a bottle is warming. And, in many of the warmers we tested, the temperature of bottle contents will continue to rise if left in the warmer after auto shut-off. This can mean overheating. Because breast milk begins to degrade significantly above at 113F/40C to 45C, removing a bottle promptly when done is important.
Making Your Selection
Taking into account the various features and options available, we scored each of the 7 warmers in our review on the following four metrics: health and safety, warming efficiency, ease of use, and ease of cleaning. These are all important factors that should be considered during your buying process.
Since a bottle warmer's main purpose is to provide your baby with a comfortably warm meal, this was a high priority in our testing. We wanted to be sure that we could toss a bottle in, tend to baby, and return to a just-right meal every time. Some of the warmers were capable of producing a consistently warmed bottle with each use, while others, like the Philips Avent Fast, varied in their results, sometimes leaving us with in an overly hot or still cool bottle. Your time is precious so we urge you to consider a warmer capable of getting the job done consistently with each use.
Ease of 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 we tested included a wide variety of "parts", ranging from one solid unit like the Kiinde Kozii, to a unit plus a bunch of extra pieces, like the Cuisinart BW-10, leaving you with quite a task on your hands. The easiest to use warmer in our testing was the Editors' Choice Award winning Kiinde Kozii; a simple, one-piece unit that didn't require a lot of prep or maintenance.
Tommee Tippee. Other bottle warmers, like the Boon Orb and the Cuisinart BW-10 offer adapters for wide-mouth and narrow bottles. We found that the Kiinde Kozii and the Chicco NaturalFit Two-in-One worked the best with all bottle types.
Another handy feature we appreciated was those warmers that included a "basket" for removing the bottle or jar of baby food in case it becomes too hot to handle. A few of the warmers we tested got carried away with the steam and would overheat the bottle itself, leaving it very hot and difficult to remove, so a basket was nice. We liked the baskets in the Boon Orb and the Cuisinart BW-10.
Ease of Cleaning
This metric is pretty self explanatory, but definitely something you'll want to consider. Although cleaning isn't always a per-use or even daily requirement, there is a certain aspect involved with keeping this type of product in proper running order. We found, that unless you spill milk on the unit, this really 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 someplace on the unit, usually in the warming chamber and/or 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. We also found that the warmers which use a reservoir system carry a higher risk for mold or mildew build-up within the reservoir itself. It is recommended that those units be cleaned out a little more often to try and avoid the possibility.
We hope that the addition of a bottle warmer to your personal baby gear line-up will help things run a little more smoothly at your house. Although it may take a few tries to get to that perfect setting, once you're there, your warmer should perform safely, consistently, and make life with baby just that much easier!