Mold In Electric Kettle: How To Clean & Prevent

There’s nothing better than waking up on a cold morning and having a nice warm cup of coffee or tea to start your day.

But what do you do when you lift the lid to fill it up, only to see what looks like a patch of green or black mold growing? Why did this happen in the first place, is the mold dangerous and do you need to throw the kettle out or can you clean it out yourself?

All these questions and more will be answered in today’s article, so for all you need to know about moldy electric kettles, keep reading.

Mold in electric kettle

Why do electric kettles become moldy?

Electric kettles can grow mold due to a combination of high moisture levels, absence of sunlight, optimal ph levels, and the potential for organic matter accumulation.

Despite being a complex organism, fungi (in this case, mold), have fairly basic needs that are not too dissimilar to our own. All it needs to thrive is a source of moisture, nutrients, and oxygen. As long as these elements are present in their environment, they can spread and multiply rapidly.

Lack of natural sunlight

Many electric kettles don’t allow any natural sunlight to enter, and as the UV rays emitted by the sun can break down and sterilize mold and mildew, this provides protection for it, making its growth far easier.


Fungi gain their nutrients by releasing enzymes that break down organic matter, which are then absorbed. Within a property, dust is the most common source of nutrients, and mainly consists of shed human and animal skin cells combined with other broken-down organic materials. The minerals and nutrients within dust are all fungi need to sustain it, and even small amounts can feed a small colony.

Dust can easily find its way into a kettle that has not been used for a while by floating down through the spout and collecting in the tank, or, directly through the top of the lid has been left open.


Fungi can grow happily through many temperature ranges. Some have the ability to grow at refrigerated temperatures, whilst others have adapted to be able to produce heat-resistant spores that can survive in temperatures up to 60-70° degrees Celsius (140° Fahrenheit).

These are the temperature extremes that fungi can survive in, but the ideal temperature for its growth, and therefore the range in which it grows most rapidly, is between 60-80° Fahrenheit (15-26° Celsius).

This also tends to be the temperature range that most US homes set their thermostat to, and so when left on a counter, a kettle will remain nearly constantly at the ideal temperature range for mold growth.

Bear in mind, however, that mold will most often form in a kettle that has been left with water in it for some time and will not grow in one that is frequently used. This is because the high temperatures the water and steam reach when the kettle is turned on will kill any mold or its spores.

Can mold grow on the bottom of a kettle?

Absolutely, if the area you keep your kettle (which is usually a kitchen countertop), is not cleaned properly and kept dry, you are giving fungi everything it needs to grow.

The base of the kettle is in constant contact with the surface of the counter, which blocks sunlight from reaching it and protects mold from the UV rays that can kill it.

A countertop is also likely to have crumbs and food debris on it, as even the tidiest of us miss spots occasionally, and if care is not taken to ensure the bottom of a kettle is dry after filling it with water, a warm, moist environment that is blocked from sunlight and has plenty of nutrients will be present right under the bottom of your kettle, making it an ideal habitat for mold to grow in.

Mold is in fact more likely to grow on the bottom of a kettle than within it, as the high temperatures do not often transfer down to the underside of its base.

What types grow?

There are four common strains of fungi that are found growing within properties, these are:

  • Cladosporium
  • Penicillium
  • Aspergillus
  • Alternaria

Without testing, it can be very difficult to be certain which strain you may have found growing, but any one of these four is particularly likely, as they grow under similar conditions.

One method you can use to try to determine which strain may be growing is to look at its texture and color. However, if you have allergies, it is really not necessary to know.

With that being said, the following are a few characteristics of the most likely strains you will find growing within or under an electric kettle.

Cladosporium – Dark coloration in brown, black, or gray-green hues. Its texture is often described as being powdery or velvet-like.

Penicillium – Brighter coloration starting out in white, then over time changing to blue, blue-green, gray-green, olive-gray, yellow, pink, or brilliant turquoise. Presents in a wool-like or velvety texture.

Aspergillus – Usually found with blue or green coloration, and with a powdery or downy texture.

Alternaria – Darker coloration, with gray-green hues seen most frequently, and with a texture that is considered to be velvety in its texture.

To reiterate, it is not important to know which strain of mold you are dealing with in order to be able to remove it from a kettle, the methods to kill fungi later in the article will be applicable to all strains.

Are they dangerous?

The strains mentioned above can indeed be dangerous, as some have the potential to create mycotoxins as a defense mechanism. These toxins have not been conclusively proven to cause the toxic mold syndrome that you may have heard of via inhalation of their spores, however, if they were to be ingested, they could certainly cause serious symptoms.

Whilst the number of spores you would be likely to come into contact with whilst attempting to remove any of these strains would be small, they can still cause symptoms in those sensitive to them, such as people with allergies or suppressed immune systems.

It is for these reasons that before attempting to clean any type of mold (whether you have allergies or not), you should always wear protective equipment such as a P1 or P2 breathing mask, goggles, and rubber gloves to prevent your skin, eyes, and lungs coming into contact with spores.

What about black mold?

Spotting black mold can be worrisome due to the media coverage which has often made outlandish claims about the severity of its toxicity. Whilst it’s true that ingesting true black mold (Stachybotrys chartarum), can cause serious illness, inhalation of its spores alone has never been proven to be more harmful than any other strain.

As previously stated, inhaling or coming into direct contact with any type of mold spores can cause allergic reactions and symptoms in nearly anyone, so this should always be avoided by wearing protective equipment.

What is the green mold in an electric kettle?

Green buildup within a kettle may not necessarily be mold at all, what it is more likely to be, is limescale formation.

Limescale is a buildup of minerals within water that condense as it boils and these form on the sides and walls of kettles in a similar fashion to stalagmites and stalactites do in caves.

The most common form of limescale we often see in kettles usually has a white color to it, but depending on the minerals present within the water, and their concentration, limescale can be white, green, pink, or brown. If the buildup has a hard and chalky texture instead of a powdery or cotton-like one, you know you are in fact dealing with limescale rather than mold.

How to clean a kettle

Fortunately, if you have left your kettle on a kitchen counter with water in whilst you went on holiday and have now come back to it with a nice layer of fungi growing in its interior, all is not lost, as the kettle can be saved with some simple cleaning solutions. Listed below are some of the tried and tested home remedies you can use to get your kettle looking like it did when you first got it home, and they are all very affordable and easy to do too.

Vinegar method

Vinegar has a dual purpose when cleaning mold out of a kettle. Not only will it kill fungi that may have accumulated whilst it was left out, but it will also dissolve limescale buildup, leaving you with a clean and fresh kettle.

Step 1. Make a solution of one part white distilled vinegar to one part water. Two to three cups of solution should be adequate.

Step 2. Fill the kettle with the mixture and boil it.

Step 3. Repeat the process once more to remove any residue limescale (any mold will have been killed by the first boil).

Step 4. Once the limescale has been removed, fill it with fresh water and boil it one last time, this will remove the scent and taste of the vinegar. If there is still a smell, rinse it out with cold fresh water until there is no longer any vinegar scent.

Lemon juice method

The acidity of lemon juice is just as effective at killing mold and dissolving limescale as vinegar, it also has a more pleasant aroma, and so is a great method to clean and freshen a kettle.

Step 1. Take two fresh lemons and cut them in half. Squeeze the juice into the kettle and look for any areas where the buildup of mold or limescale is particularly bad. Rub these areas directly with the halved lemons to ensure it is covered in their juice.

Step 2. Leave the juice to work on the limescale and mold for 10-15 minutes.

Step 3. Half fill the kettle with water and bring it to a boil. Allow it to cool before pouring the water away and inspecting the inside.

Step 4. Repeat steps 2-3 as many times as required to remove all traces of limescale and mold residue/stains.

Baking soda method

Baking soda is alkaline in nature, which when applied to mold, will both kill and lift any stains it has caused. To use this method, use the following steps.

Step 1. Take 1 teaspoon of baking soda and mix it with a small amount of water to form a paste.

Step 2. Apply the baking soda paste to the most heavily affected areas of the kettle and leave for 20 minutes.

Step 3. Pour 2 cups of water into the kettle and boil it.

Step 4. After leaving to cool, check the insides to ensure all mold and limescale are removed.

Step 5. (Optional) If after several attempts, mold or limescale remain, empty the kettle, add one cup of vinegar, to two cups of water and one teaspoon of baking soda. Boil the kettle once more and allow it to cool before checking again. This is a powerful combination that should leave your kettle looking like new.

Specific products

If you have tried a few of the above tips, but are still having trouble, there are plenty of specific products available that may be slightly more powerful than the suggested methods in this article. In most cases what we have suggested will do a perfect job, but in case of built-up limescale or a large amount of mold, you may want to try a kettle-cleaning product instead.

Is it safe to put bleach in a kettle?

No, putting bleach in a kettle is not only dangerous but can also ruin the appliance. Rinsing the kettle out after using bleach to clean it may not remove all the chemicals, and accidentally drinking these can cause a medical emergency that can require hospitalization, and in some cases, can be fatal.

Bleach is also a powerful oxidizer, and applying it to the heating element can damage it as well as other components within the kettle. Bleach is very good at killing bacteria and mold on surfaces, but it certainly is not safe nor a good idea to clean a kettle with it.

How to prevent mold buildup in a kettle

Prevention is always the best cure, and luckily, preventing mold and limescale buildup in a kettle is fairly easy and doesn’t require anything particularly fancy or expensive to do the trick. Use the following tips below to keep your kettle as clean as the day you bought it.

Empty it out after each use

Leaving water standing still at room temperature is a recipe for mold and limescale growth. Much as having water available as soon as you need it may be convenient, it is also likely to shorten the lifespan of the appliance.

After each use, pour out any remaining water and pat it dry, this will make it a far less hospitable environment for mold and mildew growth. It also gives limescale less time to accrue.

Descale it regularly

If you use your kettle on a regular basis, some degree of limescale will occur. Descaling your kettle once every three months (in soft water areas) or once every month (in very hard water areas) will prevent large amounts of limescale accumulation.

Make sure it is completely dry if storing

When planning to store your kettle away for several weeks or months, ensure it is completely dry before doing so. Any leftover moisture when mixed with dust from the location it is being stored in (such as an attic or cupboard), creates the perfect environment for mold to grow.

Use a dry cloth or paper towel to wipe down the interior and if possible, leave to air-dry for several hours before storing away. When you are ready to use it again, it will only require a wipe down and a rinse out before you can use it again.

Make use of a water softener

Very hard water areas are prone to limescale buildup much faster than soft water areas. There is also the possibility that the high level of minerals in the water may act as a source of nutrition for fungi, so lessening these is recommended.

Water softeners use filters to lessen the amount of minerals within the water passed through them, greatly slowing the rate of limescale accumulation. Some people also prefer the taste of softened water, so it may even improve your morning coffee.


Mold growth in an electric kettle is rare, as the high temperatures reached when boiling water will kill nearly all bacteria and fungi. However, if water is left standing in a kettle at room temperature for several days, or is wet when put away for storage it becomes much more likely.

Boiling a kettle with either lemon juice or vinegar mixed with water is a cost-effective and highly effective method to remove both fungal spores and remove limescale buildup.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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