Last updated: 16/10/2022

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Welcome to our large thermos flask test 2022. Here we present all the thermos flasks that we have tested in detail. We have compiled detailed background information and added a summary of customer reviews on the web.

We would like to make your purchase decision easier and help you find the best thermos flask for you.

You will also find answers to frequently asked questions in our guide. If available, we also offer interesting test videos. Furthermore, you will also find some important information on this page that you should definitely pay attention to if you want to buy a thermos flask.




Summary

  • With thermos flasks, you can keep liquids hot or cold for several hours. In most cases, this is up to 12 hours hot and up to 24 hours cold.
  • A basic distinction is made between thermos flasks made of glass and those made of stainless steel. Both types have their advantages and disadvantages and are available with different capacities.
  • With a thermos flask, you should bear in mind that they are not suitable for all liquids and that you must always clean it thoroughly so that it stays with you for a long time.

The Best Thermos: Our Picks

Guide: Questions you should ask yourself before buying a thermos flask

Who is a thermos suitable for?

A thermos flask is basically suitable for anyone who wants to enjoy their drinks at the optimum temperature at all times. The advantage of a thermos is that the contents retain their temperature for several hours.

A thermos flask is a great companion if you want to warm up after a hike in cold temperatures. (Image source: unsplash.com / Jonas Jacobsson)

This applies to both warm and cold drinks. A thermos is suitable for different places of use. You can use it at home and on the road.

If you have a thermos flask at home, you can prepare larger quantities at once and save a lot of time.

You can also use this advantage when you have to serve larger crowds, for example at a birthday party. Thermos flasks are ideal for this.

But they are also particularly suitable for on the go. You can simply take your own coffee or tea to work in the morning and save money, as coffee from home is usually cheaper.

How does a thermos flask work?

A thermos flask prevents temperature exchange with the environment. It consists of two walls. Between these walls is a vacuum, i.e. there is no air in between.

This vacuum means that less heat is lost than in a conventional jug. The inside of a thermos flask is mirrored. This also helps to maintain the temperature.

When you pour a hot drink into your thermos flask, it ensures that the heat remains in the flask. For cold drinks, a thermos prevents the warm ambient temperature from getting inside.

But there is always a certain degree of heat exchange. So the drinks do not keep their temperature forever. But depending on the quality of a thermos flask, it can last up to several hours.

What does a thermos cost?

Thermos flasks are available in many different variations. Prices vary depending on the material, design and quality. However, it is well worth investing in a high-quality thermos, as they often remain in good condition for several years.

The following table gives you an overview of the rough price ranges based on the desired quality.

Quality Price range
Low quality under 20€
Medium quality 20€ – 50€
High quality over 50€

What are the alternatives to a thermos flask?

Alternatively, you can use a porcelain jug with a textile warmer instead of a thermos.

These crocheted or knitted bonnets are put over the jug and also ensure that the contents stay warm for longer. However, the effect and duration is much better with a thermos jug.

Another possibility would be to use a teapot warmer. This is a base on which a jug can be placed. The drink is kept warm by a tea light. However, with a teapot warmer, the taste may change.

But these two alternatives would only be suitable for at home. Unfortunately, there is no good substitute for on the go. But since thermos flasks can be purchased very cheaply, this should not be a problem.

Decision: What types of thermos are there and which is the right one for you?

If you want to buy a thermos flask, you can distinguish between two different variations:

  • Stainless steel thermos
  • Glass thermos flask

Both alternatives have certain advantages and disadvantages due to the material. Depending on what is important to you and what you want to use the thermos for, one of the two thermos flasks is more suitable.

What are the characteristics of a stainless steel thermos and what are its advantages and disadvantages?

Stainless steel is a very robust and impact-resistant material and therefore very durable. This makes a stainless steel thermos perfect for on the go. Even with small dents, the thermos still works perfectly.

Advantages
  • Robust and impact-resistant
  • Well suited for on the go
  • Uncomplicated cleaning
Disadvantages
  • Insulation capacity is lower
  • Boring design

Another advantage is that you can clean a stainless steel thermos quite easily. In most cases, it can even be washed in the dishwasher, which is very uncomplicated and also saves time.

On the other hand, the temperature may not be kept at the same level for as long. The insulating capacity of these is poorer than that of a glass thermos.

If you value the appearance of your thermos, you may not be happy with the stainless steel thermos. These are only available in a very plain and boring design, namely shiny silver.

What distinguishes a glass thermos and what are its advantages and disadvantages?

Since glass can break very quickly, glass thermos flasks are unsuitable for travelling.

So if you want to use your thermos mainly for outside activities, you should rather go for a stainless steel thermos. In addition, the weight of a glass thermos is quite high.

One advantage of a glass thermos is that it is more neutral in taste than stainless steel. With stainless steel, it can happen that the steel takes on the taste and then passes it on to other drinks.

In addition, a glass thermos has the advantage that it is rust-resistant even with frequent use.

Advantages
  • Tasteless
  • Rust-resistant
  • Variety of designs
Disadvantages
  • Glass breaks quickly
  • High weight
  • Cleaning by hand

If you want to clean the glass thermos in the dishwasher, it may break. If you want to avoid this, it is better to wash it by hand. Of course, this is more time-consuming and takes more time.

With a glass version, you have many different designs from which to choose a thermos. The wide range of patterns and colours means there is something for every taste.

Buying criteria: You can use these factors to compare and evaluate thermos flasks

We will now list several factors that you can use to decide between different thermos flasks.

These criteria include:

  • Capacity
  • Closure
  • Weight
  • Insulation
  • Cleaning
  • Design

Below we explain what you should look for in each aspect.

Capacity

Thermos flasks come in different sizes. Depending on the size, the jug can of course hold more contents. You can therefore distinguish between different capacities for thermos flasks.

Depending on what you need a thermos for, you can choose between a capacity of 0.33 litres and 2 litres. If you need a thermos with even more capacity, you have to go for a pump jug. These can hold up to 5 litres.

This table can help you as a guide:

capacity cups
0.5l 2
1l 4
2l 8

If you want to use your thermos for everyday use and a lot on the go, you should choose a thermos with a smaller capacity.

Of course, you should bear in mind that the more contents you can fit into your thermos, the heavier and more unwieldy it will be.

So depending on your preferences, up to 1 litre. If you want to use the thermos mainly at home and also for parties, you should rather go for a larger thermos or a pump jug.

Closure

You can distinguish not only between different materials for a thermos flask, but also between different closures. The following closures are available:

  • Push lock
  • Rotary closure
  • Pumping closure

A pressure cap is particularly easy to use, as you only have to press once in the middle and the thermos is then already open. This closure is therefore very practical, especially when you are on the move, as you can drink directly from the jug.

A thermos flask is a must for longer hikes!

With the twist-off cap, as the name suggests, the lid has to be twisted open. This is a bit awkward, but you can use the lid as a cup.

The pump cap is found on insulated pump jugs. This closure is only available on thermos flasks with a larger capacity and is ideal for parties.

Weight

As a rule, glass thermos flasks are somewhat heavier than those made of stainless steel. However, if you only use your thermos at home, the weight doesn’t really matter.

For travelling, you should rather buy a lighter and smaller thermos. It is important to find a compromise between weight and capacity. You have to decide for yourself what is more important to you.

Insulation

As already mentioned, the insulation of a thermos also varies depending on the material. Glass thermos flasks insulate better than stainless steel thermos flasks. With better insulation, drinks can be kept hot or cold for longer.

Manufacturers generally state how long the drinks are kept hot or cold. This is usually up to 12 hours for hot drinks and up to 24 hours for cold drinks.

A teapot warmer as an alternative to a thermos flask. (Image source: unsplash.com / Siniz Kim)

However, you must bear in mind that these are only rough guidelines. For example, if you open the jug often, there will be more heat exchange than if the thermos is closed all the time.

Cleaning

There are also differences between the thermos jugs when it comes to cleaning. Some are easier and better to clean than others.

The easiest way, of course, is to choose a dishwasher-safe version. These are usually thermos flasks made of stainless steel.

For thermos jugs that are not suitable for the dishwasher, a jug with a fairly large opening is a good alternative.

The large opening makes it easy to reach the inside of the jug with a sponge or washing-up brush.

Even with dishwasher-safe thermos jugs, you should be aware that the dishwasher salt will attack the material of the thermos jug. If you want to enjoy your thermos flask for a long time, you should avoid cleaning it in the dishwasher.

You can read more about cleaning in the trivia section.

Design

Thermos flasks come in a variety of colours and patterns. This criterion should not be in the foreground, but you can of course also consider it.

In general, there is a larger selection of glass thermos flasks. They are either transparent or come in a variety of colours and designs.

Stainless steel thermos jugs are usually just shiny silver, but if you look for something, you will find it here too and can choose between different colours.

Thermos flasks come in a wide variety of very unusual designs.

Facts worth knowing about thermos flasks

Who invented the thermos flask?

There is no specific inventor of the thermos flask. The Scottish physicist and chemist James Dewar contributed a great deal. In 1983, he devised a vessel consisting of two walls with a vacuum for calorimetric experiments. This vessel was called the Dewar vessel.

By the way, the term “thermos flask” comes from the Greek word thermós (meaning warm, hot). However, since the name is a patent, in Germany they are sold under the term insulated jug.

But even before him, a physics professor from Chemnitz named Adolf Ferdinand Weinhold had invented a similar insulated vessel in the 1870s. Here, however, this container was used to solidify mercury.

The principle was further developed by the German glass technician Reinhold Burger, who was the first to achieve economic profit with a thermos flask. In 1903, he succeeded in obtaining a patent for the thermos flask. In the following years, he optimised the thermos and tried to make it more suitable for everyday use.

These were then produced in Germany from 1920 by Thermos-AG. The Amercian Thermos Bottle Company obtained the foreign rights in 1909.

What is not allowed in a thermos flask?

A thermos flask is not suitable for carbonated drinks, as the acid will attack the seal of the closure. This damages the jug and can cause it to leak.

Quickly perishable liquids such as milk must also not be stored in a thermos flask. Dangerous germs can develop here. So if you want to drink coffee with milk, you should rather use fresh milk.

Milk should not be stored in a thermos flask. (Image source: pixabay.com / Couleur)

Thermoses are also not suitable for food and baby food. If you want to keep food warm, you should rather buy a thermos container especially for food.

The only food you could keep in a thermos is clear (not pureed!) soup.

Can I take a thermos on the plane?

Whether you can take a thermos on a flight depends on the airline and destination.

An empty thermos flask in your flight baggage or hand luggage is generally allowed.
A full thermos flask in your hand luggage, on the other hand, is prohibited. You are never allowed to carry more than 100ml in your hand luggage.

In special cases, such as a thermos flask for the baby, the airport decides what you can and cannot take with you. Thermoses for babies are more likely to be allowed on long haul flights than on short haul flights.

Empty thermos flasks are usually not a problem. For full thermos flasks, it depends on the situation and the airport.

How do I clean a thermos?

You should clean your thermos after each use to avoid odours and deposits. If your thermos is suitable for the dishwasher, you can generally clean it there. However, as already mentioned, this should be avoided.

If you wash the thermos by hand, the easiest way to clean it is with a washing-up brush, a little washing-up liquid and water. In most cases, it is sufficient to rinse the thermos briefly and then dry it well.

However, if the thermos has stubborn dirt, there are a few tips to get rid of it. For example, you can clean a stainless steel thermos with baking soda. The best thing is to leave the thermos filled with water and baking soda to soak overnight.

You can clean a glass thermos flask with denture cleaner. Simply pour this into the jug together with warm water and leave to soak for about 10 minutes. Then rinse the thermos thoroughly and repeat the process if necessary.

How do I dispose of a thermos correctly?

If your thermos no longer works and you want to dispose of it properly, residual waste is the right choice. A thermos is made of different materials, so it is difficult to dispose of them separately.

Alternatively, a thermos can be taken to a recycling centre. However, you have to make an extra trip there, so residual waste is the more convenient alternative.

Image source: pixabay.com/Bru-nO

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