We test each thermos to determine how it performs with leaks, heat retention, ease of use, cleaning, etc.

Here’s the minimum you need

• Lined  with stainless steel (not glass or plastic)
• Wide mouth (a narrow mouth helps with heat retention, but makes it harder to remove some foods and to clean)
• Right size (thermoses are as small as 12 oz. or as big as 64 oz. Get the one that’s the right size for your family or use)
• Quality name (we suggest using either Thermos brand or Stanley)

Heat Retention Tests

To see how different thermoses hold in heat, we tested them by pouring boiling water into each of them and then testing the water temperature after 1 hour, 12 hours, and 24 hours.

Here are the results:

• Electric Kettle: 3 minutes 23 seconds
• Microwave: 6 minutes 20 seconds
• Gas stove: 6 minutes 51 seconds

As you can see, you’ll be sitting around a lot longer waiting for water to boil on the stove or in your microwave.

Also, it makes me nervous to boil water in the microwave because it can become super heated and explode when you go to remove it from the microwave. Because of this, you’ll always want to place something – a chopstick, wooden stir stick, etc. – into the water. This will provide an irregular surface so that bubbles can form and be released in the boiling process.

Boiling water on the stove is problematic as well, especially when you’re trying to pour the boiling water from the pan into a small opening of the thermos. An electric kettle has a pour spout that can direct the boiling water exactly where you want it to go.

I’ve owned a used a Breville electric kettle for a years and I’ve been really happy with it. I’ve also heard good reports about the Aroma-brand kettles. I like buying from Amazon because they have a great selection and I usually can’t find kettles in my local department stores.