Nuby RapidCool Review: How It Works & Is It Worth It?

Fed up with waiting for a baby’s bottle to cool while they become increasingly furious about the delay? I have been there. Austin wasn’t really a screamy baby. Autumn, on the other hand, made her feelings known. If she was tired, we needed to get her into her cot quickly. If she was hungry, waiting 15 minutes for a freshly made bottle to cool was not something she considered acceptable. Autumn was combi-fed, with a mixture of breast milk, expressed milk and formula. She wasn’t particularly fussy about how her milk arrived, but she did expect it to arrive promptly. That was why I was interested when Nuby offered us its RapidCool Kit to try.

Originally published 12 September 2022. Last updated 27 August 2026

Disclosure: Nuby gifted us the RapidCool Kit, but all opinions and experiences are my own. This article contains affiliate links. If you buy something through one of these links, I may receive a small commission at no additional cost to you.

Check the latest price for the Nuby RapidCool on Amazon.

The Nuby RapidCool is designed to cool a freshly prepared formula feed to drinking temperature in as little as two minutes, although larger feeds can take longer. After using it ourselves, I could see why so many formula-feeding parents describe it as a lifesaver—particularly for night feeds and bottles away from home.

My Honest Nuby RapidCool Review

Before using the RapidCool, we prepared formula with freshly boiled water and then placed the bottle in a jug of cold water. This worked when we could anticipate Autumn’s feeds, but cooling a bottle could take around 15 minutes.

The RapidCool made that process much quicker. Instead of waiting beside a jug and repeatedly checking the bottle, the flask absorbed the heat from the freshly prepared feed. Its digital lid indicated when the milk had cooled sufficiently.

My initial impression was that the system sounded slightly complicated. There were cooling flasks, an insulated hot-water flask and red, amber and green indicators to understand. Once we had used it a couple of times, however, the process felt simple.

There are some important practical considerations. A RapidCool needs time to reset after each use, and it must be cleaned and sterilised before being used for another formula feed. I would therefore recommend a twin pack or the complete kit if you expect to prepare bottles regularly throughout the day.

Nuby RapidCool Pros and Cons

What I liked:

It cooled Autumn’s formula considerably faster than a jug of cold water.
It was quiet enough to use during night feeds.
It was compact enough to carry in a changing bag.
The digital lid removed some of the guesswork from cooling.
It did not require filters or an electrically powered preparation machine.
The insulated flask made preparing a fresh feed away from home more manageable.
The digital lid uses a long-life lithium battery that does not require charging.

Things to consider:

Each RapidCool can only be used for one formula feed before being cleaned and sterilised.
The cooling flask needs at least three hours to reset after contact with boiling water.
Steam sterilising increases the reset time.
The measurement markings inside the flask can be difficult to see in some lighting.
The feed can continue cooling if it is left in the flask after the indicator turns green.
You still need to follow the formula manufacturer’s instructions carefully and test the milk before feeding.
If your baby feeds frequently, one cooling flask may not be sufficient.

How Does the Nuby RapidCool Work?

The RapidCool contains heat-absorbing material within the walls of its flask. When hot liquid is added, this material draws heat away from the feed and helps it cool much more quickly.

The digital lid contains a temperature sensor. After adding the freshly boiled water and formula, you secure the lid, mix the feed and invert the flask so that the liquid reaches the sensor.

The indicator displays amber while the feed is still too hot. When the Nuby logo turns green, the feed should be ready to transfer into a sterilised bottle.

It is important to turn the flask upside down for at least 10 seconds so that the liquid touches the sensor. If the milk does not make proper contact with the lid, the displayed temperature may not be accurate.

Even when the indicator is green, always test a few drops on the inside of your wrist before feeding your baby. The milk should feel warm or cool, not hot.

How to Use the Nuby RapidCool

These are the current basic instructions supplied by Nuby:

Wash your hands and clean the preparation surface.
Boil fresh drinking water from the cold tap.
Measure the required amount of freshly boiled water into the RapidCool using its internal markings.
Add the exact quantity of formula specified by the formula manufacturer.
Secure the digital lid and mix the feed thoroughly.
Turn the flask upside down for at least 10 seconds so the liquid reaches the temperature sensor.
Stand the flask upright and wait for the Nuby logo to turn green.
Transfer the feed into a clean, sterilised bottle.
Test the temperature on the inside of your wrist before feeding.

Nuby says cooling normally takes approximately two to five minutes, depending on the size of the feed.

When Autumn was little, I found the markings inside the flask difficult to read in our kitchen lighting. I preferred to measure the water in her sterilised bottle first, add the correct formula and then transfer the mixed feed to the RapidCool.

If using a different method from the current instructions, check the latest guidance supplied with your RapidCool. Product instructions can change, and preparing formula correctly is more important than saving an extra minute.

Does the Nuby RapidCool Follow NHS Guidelines?

Nuby states that the RapidCool method conforms to NHS formula-preparation guidance.

The NHS advises preparing one formula feed at a time using freshly boiled drinking water. The water should still be at least 70°C when combined with powdered formula because formula powder is not sterile and can occasionally contain harmful bacteria.

The RapidCool uses freshly boiled water to prepare the feed and then cools it afterwards. It does not rely on adding cooled water to the powder.

Parents should still follow both the instructions supplied with their formula and the latest NHS guidance on making up baby formula. Never change the water-to-powder ratio, and pour away any milk left in the bottle after a feed.

If your baby uses a specialist or anti-reflux formula, check its preparation instructions or speak to your health visitor because some specialist formulas may require a different method.

Is the Nuby RapidCool Safe?

The RapidCool is designed to prepare and cool a fresh formula feed using water hot enough to reduce the risk posed by bacteria in formula powder.

Its safety depends on using it correctly. You need to:

Use freshly boiled water.
Measure the water and formula precisely.
Clean and sterilise the RapidCool between formula feeds.
Allow it to reset fully before using it again.
Invert the flask so the feed reaches the temperature sensor.
Wait for a consistent green reading.
Test the feed on your wrist before giving it to your baby.
Inspect the flask, seal and lid regularly for damage.

The outside of the RapidCool may become warm while it absorbs heat. Nuby advises adults to handle it carefully and stop using it if it shows signs of damage or weakness.

How Long Does the Nuby RapidCool Take to Reset?

The RapidCool needs a minimum of three hours to reset after it has been used with boiling water.

Heat activates the material inside the wall of the flask. If the RapidCool is used again before it has recovered, it may not cool the next feed properly and can become unusually hot to hold.

This is one of the main reasons the complete RapidCool Kit includes two cooling flasks. One can reset while the other is available for the next feed.

Washing the flask in very hot water can also activate its cooling material. Nuby currently recommends washing it in warm rather than very hot water.

If you steam-sterilise the RapidCool base, Nuby advises waiting at least four hours from the end of the sterilising cycle before using it again.

How to Clean and Sterilise a Nuby RapidCool

The cleaning advice for the base and digital lid is slightly different.

To clean the cooling flask:

Separate the flask, seal and lid.
Wash the components promptly after use.
Use warm, soapy water and the appropriate cleaning brush.
Rinse as directed in the product instructions.
Sterilise the base using a compatible method.
Allow everything to drain and dry hygienically.

Nuby says the RapidCool base can be sterilised using cold-water, UV or steam sterilisation, or in a dishwasher. Do not steam-sterilise it in a microwave.

To clean the digital lid:

Wash the lid using warm, soapy water. Nuby advises sterilising the digital lid using cold-water or UV sterilisation rather than steam.

Cold-water and UV sterilisation should not activate the cooling material. Hot washing or steam sterilisation can affect how soon the RapidCool is ready to use again.

Always follow the care leaflet supplied with your particular model, especially if your RapidCool differs from the version shown in my photographs.

How Long Does a Nuby RapidCool Stay Sterile?

There is no single guaranteed number of hours for which an assembled RapidCool will remain sterile.

After sterilising, allow the components to drain as instructed and assemble them without touching surfaces that come into contact with the feed. Keep the flask closed until needed.

If the inside, seal or lid becomes contaminated, or if you are unsure how it has been stored, clean and sterilise it again before preparing a feed.

When we used a cold-water steriliser, we washed the RapidCool immediately after use, completed the sterilising cycle and reassembled it ready for the next feed.

How Long Does the Nuby Insulated Flask Keep Water Hot?

The insulated flask supplied with some RapidCool kits is intended to carry freshly boiled water for feeds away from home.

Nuby says that, when preheated correctly, its insulated flask should keep water above a suitable formula-preparation temperature for at least two hours.

To preheat it:

Fill the insulated flask with boiling water.
Leave it briefly so the inside becomes hot.
Empty it carefully.
Refill it with freshly boiled water and seal it immediately.

The RapidCool digital lid can be attached to check the temperature. A red Nuby logo indicates that the water is still hot enough according to the product instructions. Amber or green means it should not be used to prepare powdered formula.

The NHS advises that water used to make formula must still be at least 70°C. If you cannot prepare a fresh powdered feed safely while away from home, ready-to-feed liquid formula is an alternative.

Does the Nuby RapidCool Keep Water Hot?

The cooling flask itself does not keep water hot—it is designed to do the opposite.

The separate insulated flask included in some kits keeps freshly boiled water hot until you need to make a feed. It is easy for the two flasks to become confused when researching the product, so check exactly which RapidCool set you are buying.

Can You Use the Nuby RapidCool More Than Once?

You can use a RapidCool repeatedly over its lifetime, but it makes one formula feed at a time.

After formula has been inside the flask, it needs to be cleaned and sterilised. It must also complete its reset period before it can cool another feed effectively.

If your baby needs another bottle within three hours, you will need a second RapidCool or a different safe method of cooling the feed.

Does the Nuby RapidCool Need Charging?

No. The digital lid contains a long-life lithium battery and does not require charging.

Nuby does not specify an exact battery lifespan because this will vary with use. Inspect the lid regularly and contact Nuby if the display stops responding or becomes unreliable.

Why Is My Nuby RapidCool Always Green?

A permanently green display can occur if the feed has not reached the temperature sensor or if the flask has not reset properly.

Try the following:

Make sure the RapidCool has had at least three hours to recover.
Keep it away from direct sunlight and other heat sources while resetting.
Secure the lid properly.
Turn the flask completely upside down for 10 seconds.
Return it upright and check the indicator again.
Repeat the inversion before relying on the final reading.

If the lid remains green when freshly boiled water is added, stop using it to prepare feeds and contact Nuby. Do not rely on a reading that appears inconsistent with the actual temperature.

Can You Use the Nuby RapidCool for Breast Milk?

The RapidCool can physically cool liquid, but it is primarily designed for making and cooling powdered formula.

Expressed breast milk normally does not need to be heated before a baby drinks it. It can be served at room temperature or cold if your baby accepts it. If you choose to warm expressed milk, warm it gently and avoid making it so hot that it then needs rapid cooling. Take a look at my post about the best bottles for breastfed babies for some great product recommendations.

Follow current NHS advice on storing, warming and using expressed breast milk. If you are unsure, speak to your midwife or health visitor.

Is the Nuby RapidCool Worth It?

For us, the Nuby RapidCool was worth having.

Its biggest advantage was speed. When Autumn was hungry, reducing the cooling wait from around 15 minutes to a few minutes made feeds significantly less stressful. It was particularly helpful when her feeding pattern was unpredictable and when we needed to make a fresh bottle away from home.

I also liked that it did not use filters and did not require a powered machine on the kitchen worktop. My husband appreciated the relatively simple cleaning routine, although the reset time and need to sterilise between feeds meant that having two cooling flasks was much more practical than relying on one.

It may be less useful if you only prepare occasional bottles, are happy cooling them under cold running water, or normally use ready-to-feed formula while away from home.

For parents preparing powdered formula regularly, especially those dealing with impatient night-time feeds, it can be an extremely useful piece of kit.

My Final Nuby RapidCool Verdict

The RapidCool initially looked more complicated than it turned out to be. Once we understood the colour indicators, reset period and cleaning requirements, it became a straightforward part of preparing Autumn’s formula.

Its limitations are worth understanding before buying. It cannot immediately be reused; it needs proper cleaning and sterilising, and you must turn it upside down for the temperature sensor to work correctly.

Despite that, it did exactly what we needed: it cooled a safely prepared formula feed much faster than our old jug-of-water method. For a hungry baby who did not enjoy waiting, that made a genuine difference.

Check the current price and availability of the Nuby RapidCool on Amazon.

Always follow the latest instructions supplied with your product, your formula manufacturer’s directions and current NHS bottle-feeding guidance.