Zojirushi Stainless Steel Thermos
The best thermos can be used for a variety of situations but mainly it keeps your hot liquids warm and cold beverages cold. Officially, they are called vacuum flasks or insulated bottles, but since Thermos was the company to make them popular, the name caught on and has become the industry standard. Thermoses are basically a bottle with a thick layer of insulation on the inside.
This insulation keeps hot thing hot and cold things cold. There is a huge misconception that a thermos is only good for keeping coffee, soups, and hot meals hot. Many people do not realize that the best thermos can also keep a cool drink cold. Thermoses can vary depending on insulation, durability, and price. They are not all created the same and there is a big difference between an expensive thermos and a cheap one. If you are interested in something bigger to keep your food and beverages hot or cold for a long time, you should read our ice chest reviews.
Best Thermos Reviews
- Zojirushi Stainless Steel Thermos (Top Pick)
- Thermos Stainless King Bottle
- Eco Vessel Boulder Water Bottle
- Stanley Classic Vacuum Bottle
- Hydro Flask Double Wall Vacuum Insulated Stainless Steel
Zojirushi Stainless Steel Thermos
If you want the best thermos that provides great insulation, you want to look into the Zojirushi Thermos. It is made of stainless steel with an air tight lid that seals with a safety lock. The lid is durable and absolutely will not leak any liquids. We really like the safety lock feature on the Zojirushi because it stops you from having accidental spills.
In terms of design and build quality, we can’t really point out anything negative. We found the opening is just enough to let ice cubes slip but not so big as to make it hard to pour liquids out. The stainless steel outer shell not only looks impressive, but also it makes the entire bottle extremely durable and adds a layer of insulation. It certainly does not feel cheap when you hold this thing.
If you ever feel worried about breaking this thermos rest assured that it comes with a 5 year warranty. Our only real complaint about the design is that since the opening is a bit small, it makes cleaning difficult. You will need to use a bottle scrub brush to clean it thoroughly. Also the spring action on the lid is a bit flimsy and feels like it could break any moment.
Despite its minor design flaws, in terms of insulation, the Zojirushi is the best thermos for tea, coffee, or cold drinks. We think some smart Japanese engineering went into the design and construction of this thermos because it has stellar insulation. After testing this thermos against many others in our lab, the insulation test results showed Zojirushi as the winner across the board.
It holds the test record for keeping both hot things hot and cold things cold the longest. It has a double wall stainless steel vacuum insulation that diminishes the loss of heat through convection currents. Compared to the Thermos brand, Zojirushi outshined its competition in terms of insulation. It kept ice cubes longer by around six hours and coffee warmer by around three hours. Â We also like the steel coating inside the thermos, which is easy to wash and does not soak in any scents.
Thermos Stainless King Bottle
In terms of overall design, we think Thermos Stainless King is the best thermos. Since the 1900s, Thermos has been making insulated water bottles. They became so good at it that the company name became the industry standard and people started calling them thermos instead of vacuum flasks. These days, the game has changed a bit and more companies have entered the competition.
As we mentioned before, we really like the design and build quality of the Thermos Stainless King. First of all, this thermos just looks absolutely gorgeous. With the sleek black and stainless steel design, it belongs right next to your iphone and ipad at Starbucks. There is a lot of functionality as well. The lid twists off and becomes a nifty cup for your coffee or beverages. The stopper at the opening of the thermos is designed so that you can slightly twist it to let liquids out slowly but it won’t be enough pressure to let the entire bottle slip out.  The stopper creates an air tight space on the inside and stops all leaks, more than the Zojirushi.
The Thermos Stainless King also has incredible insulation. It can keep your drinks hot for 12 hours and your drinks cool for 24 hours. In between the inside and the outside is an airless space called a vacuum that acts as insulation. This vacuum will slow the transfer of heat from inside to outside. The sound engineers who made the Thermos Stainless King made sure to figure out a way to minimize heat loss through designed an air vacuum.
Although we admire their efforts, we give the gold medal to Zojirushi, whose insulation is slightly better. Although the difference is not huge, Â we think that those who want the best thermos for insulation should look for the Zojirushi. In terms of overall package, design, and functionality, Thermos Stainless King wins. It is also the best food thermos and great for soups as well.
Eco Vessel Boulder Water Bottle
Eco Vessel makes the best thermos if you want an eco-friendly thermos bottle that is also recyclable. It started in Boulder Colorado and manufactures a strong line of thermos that are free of BPA, phthalates, liners, and other harmful chemicals to the environment. The outer shell is made of premium #304 stainless steel and is very durable.
We really like the design of this thermos, which is also tailored towards outdoors enthusiast. It has a cap with a bendable handle attached to the lid. The handle can be hooked into a carabineer or strapped to your backpack for storage. One of the pitfalls of this lid is that it does not shut the contents inside the thermo air tight. There is a bit of leaking if you toss this thing around, but we don’t think this is a huge issue.
On the insulation front, Eco Vessel advertises a triple insulated wall. Normal premium thermoses have two walls of stainless steel separating the inside from the outside, but Eco Vessel incorporates three walls. Because of all the hype surrounding this relatively new company, we had to try it out for ourselves. While we do think that the triple insulated wall is a marketing tactic, we don’t doubt its ability to insulate.
We find the insulation power on par with Thermos Stainless King, being able to kept cold things cold for about a day and hot thing hot for 12 hours. Although the company reports 36 hours of cold insulation, we cannot verify this is true through our stress tests. Overall, this is a solid thermos for outdoor enthusiasts who are also eco-conscious.
Stanley Classic Vacuum Bottle
The Stanley Vacuum Flask is a classic and the best hot food thermos. These were one of the best-selling thermoses back in the day. Now it is certainly making a coming back as many people now prefer the retro design. Even though it looks rustic, it still functions just as good as any vacuum flask on the market. It keeps hot drinks hot for an entire day and cold drinks cold for even longer. You can get insulated lid that also doubles as a soup or drinking cup. The entire unit is leak proof, as long as you take the necessary precautions to seal it properly.
In terms of durability, we can certainly vouch for the Stanley Vacuum Flask. It is made of 18/8 stainless steel, so it won’t rust and is naturally BPA free. It has a tough Hammertone powder coating that can take a beating wherever you go. We tested this unit out in our lab by dropping it and slamming it around. While it certainly did take a minor beating in terms of paint chips falling off, we found it really hard to make a dent in the thermos.
The Stanley Thermoses come in many different sizes ranging from a 2 quart or 1.9L flask to a 16 oz flask. Keep in mind that the insulation time is different for various sizes. The largest thermos can keep liquids hot for 32 hours while the smallest one can only keep liquids hot for 15 hours. For cold content, you get 15-32 hours. And if you have iced content, the range is even longer at 60-160 hours.
The best part about the Stanley Thermos is the nostalgic feeling it gives you when you are using it. It is great to take with you on fishing and camping trips. And if you beat it up it should not be a problem. It may look even better with some dirt around the edges and the paint chips peeling. The Stanley thermos has been around since 1913 and this model hasn’t changed. It is still great at keeping your liquids and solids hot and cold. It is the best thermos for soups and food. Also it just looks cool.
Hydro Flask Double Wall Vacuum Insulated Stainless Steel
Hydro Flask sells a great product if you want a simple water bottle or thermos that you can take with you everywhere. It is the best wide mouth thermos we have tested. This thermos is certainly not one of these giant thermoses made for multi-day camping or hiking trips. The Hydro Flask is more suitable to bring with you to the gym or to a sports event.
It doesn’t have the same level of insulation as a proper Thermos or Stanley, but for intra-day events. For keeping liquids hot, The Hydro Flask will insulate up to 6 hours and up to 24 hours for cold drinks.
The bottle is made of a pretty nice premium material. It has non-toxic BPA-free plastics and 18/8 food grade stainless steel. There is a proprietary powder coating on the outside so that your bottle stays slip free. It really is a nice grip as advertised and the non-slip coating definitely doesn’t peel off easily. In terms of caps, you get a standard wide flex cap. However, if you want a different style cap, Hydro Flask sells those as well. You have a wide straw lid cap and a wide flip lid as well. Unfortunately, these are sold separately. We recommend the wide flex cap if you want something to hook the flask onto.
The Hydro Flask comes in four different sizes and all have wide mouth bottles. You have a 18 oz, 32 oz, 40 oz, and 64 oz. Luckily, all of them are pretty lightweight so you won’t feel burdened while holding them. Also, the color selection is awesome. You get to choose from one of 17 different colors. We really like these colors and none of them are plain. Overall, if you want a great portable thermos that looks stylish and can be used for intra-day events, you should consider the Hydro Flask. And because of its wide mouth, it is also the best thermos food jars for kids lunches, soups, and keeping things hot.
Finding the Best Thermos
Not all thermoses are made the same. In this industry, you can have anything from a thermos given away at a street fair to a top of the line professional grade thermos. The main factors in choosing the best thermos are insulation, durability, and price. Insulation is probably the most important determinant for a lot of potential buyers.
Most people want a thermos that will keep their coffee hot all day or their sodas cold at the beach. To find the best thermos for insulation, generally look for ones that have at least a double wall stainless steel vacuum. This makes the flow of heat difficult between two stainless steel plates and a vacuum space in between them. The best insulation is a vacuum, not foam pads as you may think. The way that the steel plates are set up and the amount of vacuum space compared to the volume of the thermos also greatly determines insulation ability. This is where great engineering comes in handy.
Durability is another important factor when trying to find the best thermos for kids lunches, hot food, soup, or liquids. If you are going to spend money on a good thermos you want to make sure it doesn’t crack if you drop it. You want one with good grip and a solid lid that closes very tight. Also, you want to make sure it doesn’t leak any fluids and is also easy to wash. Additionally, look for a thermos that is lightweight and can be transported easily. Finally, you probably want a thermos that looks nice and has a good warranty.
How Does a Thermos Work?
The basics of how a thermos works goes back to physics and the first law of thermodynamics. The first law states that energy can be transferred from one body to another, but it cannot be created or destroyed. There are three ways that heat can be transferred: convection, conduction, and radiation.
Now what the first law of thermodynamics implies is that when two bodies are together, they will transfer heat to each other until they reach a thermal equilibrium. Simply stated, heat transfers from a warm state to a cooler state. This law explains why ice melts and hot liquids eventually cool down.
Ice is in the same system as your room, and they both transfer heat energy to each other until they reach an equilibrium temperature. In other words, heat will transfer from the room to the ice and the ice will also transfer energy to the room.
But since the room is infinitely larger than the block of ice, room temperature will be lowered by a faction of a degree which won’t be noticeable. Since the block of ice is small, its temperature is raised significantly as its temperature becomes the room temperature. In the meantime, the ice is melted and the water becomes room temperature.
So now we know that whenever two bodies are in contact they will try to reach an equilibrium temperature. This transfer of heat is inevitable. However, we can slow it down through an insulator. Insulation is simply a material that lies between the two forms that slows down the transfer of heat. Highly density foam is a great insulator that is used in many coolers.
It greatly slows down the natural transfer of heat from a warm body to a cooler body. Â The denser the material, the slower heat will transfer. The best insulator happens to be a vacuum, or a space devoid of everything including air. It turns out heat transferred through a vacuum at an extremely slow pace. Inside a thermos bottle is actually a vacuum, or empty space.
This empty space is enclosed by two steel walls, one on the outside and one on the inside to hold your liquid. Since a pure vacuum is incredibly difficult to achieve, the thermos will always have some very small leaks that make the vacuum a bit less effective as an insulator. The cap and lid is normally where a lot of the heat escapes. And everytime you open up the thermos, some heat will also escape.
Why do you want a thermos?
The best thermos is used to keep any object at a steady temperature. It is not limited to only hot drinks, tea, coffee, or soup. It will act as a cooler and hold cold liquids. Or if you want, you can also use it as a water bottle. Whatever you do, don’t be fooled by a company and their marketing.
Many companies try to promote different products: a thermos to keep hot things in and a water bottle to keep your drinks cool. They are the exact same thing but with a different name. Don’t be fooled by this.
Also, you maybe wondering why thermoses advertise they can keep cold way longer than they can keep hot. This is because cold liquids are much closer to room temperature than warm liquids. Room temperature is around 70 degrees Fahrenheit and water boils at around 212 degrees Fahrenheit while water freezes at 32 degrees Fahrenheit.
As you can see here, it is much easier for something hot to cool down to room temperature because when there is a bigger temperature difference, heat will transfer faster. Since ice is much closer to room temperature than a hot boiling liquid, it will take longer to melt ice than to cool down boiling water.
