Bottle Warmer vs Microwave vs Hot Water (incl. Kettle)

Balint Horvath, PhD

Writer, parent, and veteran of baby feeding battles.


Trying to compare using the bottle warmer vs microwave methods with the hot water solution?

As parents, we were always on the lookout for the easiest, fastest, and safest options! Here’s a full comparison article to help you choose the most suitable one for you. 

Bottle warmers are convenient, safe, efficient, and easy to use. They’re also fast, warming bottles up within 4 to 6 minutes. The microwave warming method isn’t recommended for safety reasons while using hot water to warm bottles is cost-effective and simple but time-consuming. 

Key takeaways

  • Bottle warmers have many benefits including convenience, safety, and ease of use, and are best for preserving nutrients in breast milk but can be expensive.
  • Warming baby bottles in microwaves isn’t the safest method as it increases the risk of hot spots. 
  • Using the hot water method is cost-effective and simple to use but takes more effort and time.

Bottle warmer vs microwave vs hot water comparison for warming baby bottles

Warming MethodProsCons
Bottle warmer– Quick
– Heats to the right temperature
– Preserves nutrients 
– Safe
– Multifunctional
– Easy to use
– Expensive
– One size doesn’t fit all bottles
Microwave– Quick– Creates hot spots
– Destroys nutrients
– Can damage bottles
Hot water– Cost-effective
– Uses the kettle, stovetop, or microwave to heat water
– Safe
– Preserves nutrients
– Time-consuming
– Scalding risk for handler
– Difficult to control temperature

Pros and cons of bottle warmers

Bottle warmers are many times needed as they’re efficient, safe, and convenient to use. They can be used for warming infant formula and breast milk. But, is it an expense you want to pay for when there are SO many other things you need for your bottle-fed baby? 

We loved our portable bottle warmer with rechargeable batteries which we took with us whenever we went on hiking trips. Weigh up the pros and cons and decide for yourself if it’s worth having a bottle warmer in your kitchen, or on the go.

Pros of bottle warmers

  • Quick and steady heating: Bottle warmers reach a steady temperature quickly. The bottles are warmed to the right feeding temperature faster than alternative methods. 
  • Safe: You don’t need to worry about dangerous hot spots forming in the milk which could scald your baby’s mouth. 
  • Preserves nutrients: Prevents overheating breastmilk which alters the composition of the nutrients essential for your baby’s healthy growth and development.
  • Defrosting: Can be used to defrost expressed frozen breast milk. 
  • Easy to use: All you have to do is switch on the appliance and the rest is done for you. Smart models let you operate the appliance from your smartphone or app. 

Cons of bottle warmers

  • Doesn’t fit all bottles: Baby bottles come in all sizes and shapes and some don’t fit in a bottle warmer unless you stick to the same brand. Check out my article on the best bottle warmers for various brands to get the right fit for your bottles. 
  • Expensive: This can be a costly option if you’re on a tight budget. Cheaper brands aren’t always reliable and don’t last as long as more expensive quality products.

Pros and cons of using a microwave

Nearly every household has a microwave in the kitchen for warming, defrosting, and even cooking food. But, can it be used to warm baby bottles? 

According to La Leche League International, heating human milk in the microwave causes it to:

  • Destroy vital immunological components
  • Decrease in anti-infective properties
  • Denaturize and deactivate the milk’s bioactive proteins
  • Decrease in fat content

Pros of using the microwave

  • Fast: The milk warms up quickly and saves you time heating up water on the stovetop.
  • Cost-effective: Saves you from spending money on a bottle warmer.

Cons of using the microwave

  • Hot spots: Infant formula or breastmilk doesn’t warm up evenly and hot spots often form which can burn or scald your baby’s mouth.
  • Destroys essential nutrients: The vitamin and mineral content of breast milk is destroyed or altered with uneven heating.
  • Hazardous: Other dangers associated with this warming method include exploding bottles and the breakdown of the bottle’s materials. You also risk burning your hands when removing a hot bottle of milk from the microwave. 

Pros and cons of using hot water 

Warming baby bottles in hot water is an age-old tradition that can still be used today! The common method involves standing the bottle in a jug, bowl, or saucepan of hot water until the formula or breastmilk reaches the right temperature. You can test the milk by putting a few drops on your wrist or the back of your hand. 

Pros of using hot water

  • Uses common kitchen items: All you need is a kettle, microwave, or stovetop to heat the water before pouring it into a bowl or jug to warm the bottle.
  • Defrosting: This method can be used to defrost expressed frozen breast milk.
  • Portable: Fill a thermos flask with hot water and you’re good to go when warming baby bottles away from home!
  • Cost-effective: You don’t need to buy additional equipment or kitchen items to use this method. 

Cons of using hot water

  • Time-consuming: Formula or breast milk takes longer to warm up to the right feeding temperature. You also have to wait for the water to heat up which can be stressful when you have a hungry baby on hand!
  • Scalding risks: Handling hot water with a crying baby can be hazardous and you could risk scalding yourself in the process.
  • Difficult to control temperature: It’s not easy to get the right temperature and you may need to test it a few times before feeding your baby.

How to use a bottle warmer to warm bottles

Each brand will have its own instructions for using the bottle warmer – read the manufacturer’s guidelines to use your appliance correctly. However, their designs are mostly similar and simple to use. 

  • Step 1: Fill the baby bottle to the right measurement and put the nipple and cap on.
  • Step 2: Place the bottle in the warming chamber. 
  • Step 3: Fill the chamber with water. Don’t overfill the chamber – the water level must reach the line marked inside the chamber. 
  • Step 4: Turn the dial for the right warming temperature and switch on. 
  • Step 5: Remove the bottle when the cycle finishes – most devices warm up bottles within four to six minutes.
  • Step 6: Give the bottle a gentle swirl to remove any hot spots and test the temperature with a few drops on your wrist.

Watch this video on how to use a portable bottle warmer.

How to use a microwave to warm bottles

If you decide to use a microwave to warm bottles take some precautions. Use only microwave-safe bottles and give the warmed bottle a good stir or swirl to remove hot spots before feeding your little one. 

  • Step 1: Fill the bottle to the right measurement – don’t overfill as it can cause the contents to spill over during warming. NEVER warm less than 4 ounces of formula or breast milk as this increases the risk of hot spots.
  • Step 2: Place the bottle inside the microwave. Make sure it stands upright and don’t put the teat or lid on as it can cause the bottle to explode. 
  • Step 3: Heat 4 oz bottles for no longer than 30 seconds at full power. Larger 8 oz bottles mustn’t be heated for more than 45 seconds at full power. 
  • Step 4: Remove the bottle carefully to prevent scalding and use a clean teaspoon to stir the contents a few times.
  • Step 5: Place the nipple securely on the bottle and shake it a few times to remove hot spots. 
  • Step 6: Test the temperature by adding a few drops to the wrist before feeding your baby. 

How to use hot water to warm up bottles 

There are a number of ways to use hot water to warm up bottles. 

  • Step 1: Boil water in a kettle, on the stovetop in a saucepan, or in a bowl in the microwave.
  • Step 2: Fill the bottle to the right measurement. Place the nipple and cap on it.
  • Step 3: Pour hot water from the kettle into a jug or bowl and stand the bottle in it. If you’re using the stovetop method. remove the pan before placing the bottle in the hot (NOT boiling) water. Remove the bowl from the microwave before standing the baby bottle in it. 
  • Step 4: Leave the bottle in the hot water for no longer than 15 minutes.
  • Step 5: Remove from the hot water and give the bottle a gentle swirl to warm the milk evenly.
  • Step 6: Test the temperature of the milk by putting a few drops on your wrist before feeding your baby.

Comparing alternative methods 

When comparing the bottle warmer vs hot water warming methods consider which option is safe before considering convenience, speed, and ease of use. 

Bottle warmer vs kettle

First, don’t ever consider placing a baby bottle inside a kettle! This is a major safety hazard and you run the risk of your kettle malfunctioning. 

The only time you can use the kettle for warming bottles is to heat up the water.

When comparing bottle warmer vs kettle warming options, consider the following:

  • Every home has a kettle making it a cost-effective solution if you can’t extend your budget to include a bottle warmer.
  • Bottle warmers heat formula or breastmilk efficiently and to the right feeding temperature. 
  • Bottle warmers heat bottles within four to six minutes with minimal fuss compared to kettles which take more time and effort, 
  • Both methods are safe to use and prevent the risk of hot spots forming in the milk.
  • Both methods help to preserve nutrients in breast milk. 

Bottle warmer vs warm water dispenser

Warm water dispensers are handy alternatives to kettles. They keep water hot throughout the day, are energy-efficient, and save you time waiting for the kettle to boil. Hot water dispensers heat water keeping it at around 94℉ which is less than the boiling point. Bottle warmers can be set at higher temperatures but around 98℉ is best for breastmilk

Is it better to buy a bottle warmer or a warm water dispenser? My answer would be yes because it’s:

  • Affordable
  • Smaller and more portable
  • Less time-consuming  


Knowing how to warm baby bottles safely is important and I find the bottle warmer most convenient. But, using the hot water warming method works for many, too so don’t discount this option either!

As a recommendation for another article to read, have a look at the difference between using a bottle warmer vs a bottle sterilizer. You might be surprised of some of the important differences between the two.

If you want to get a bottle warmer, here are two popular models I covered in another article – Baby’s Brew vs Munchkin Bottle Warmers.

Photo of author


I’m Balint, founder of this site and a father (and dad) to a baby-turned toddler. I found the world of babies so fascinating that I started a blog dedicated only to that topic. By the way, I studied physics, engineering (PhD, MSc), and therefore I do a thorough research when I write about something. Since it’s a blog, of course I also write about my personal experiences.

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