Immersion heater?

Getting the voltage right.

If you are staying in a hotel in Europe you will either have a kettle in your room or you can ask for hot water at reception.

I have never needed an immersion heater and been a traveller since the mid 1980s.

Hansen, I haven't used one in a while, but I dont think brand is important. It's not a high-tech item, without any distinguishing features, and they all work the same. They lasted until I couldn't find them, and got another. Just unplug them before you pull them out of your cup.

I always carry one when we travel, along with an insulated mug I can use it in.

Not all hotel rooms provide a kettle; and some provide a Nespresso or similar coffee maker which does not actually boil the water. An immersion heater will.

Brand does not matter, but make sure it is dual voltage or 220-240v. If it has a U.S. plug (as almost anything you buy on Amazon or elsewhere in the US will), you just need a plug adaptor appropriate for the country you are visiting.

The most important thing, as mentioned above, is to immerse it in the water before you plug it in, and be sure to unplug it BEFORE you remove it from the water. Even a second out of water will burn it out if it is plugged in. I have lost two that way and still have to pay strict attention when using it.

My current one is a larger European model that I bought in Bologna last September to replace the one I burned up our last morning in the Dolomites. I like it and hope it will last a long time.

An immersion heater is a very simple device so there is really no need to spend a lot of money on a fancy brand. But if it's for European travel, I'd suggest buying one in Europe. Then it will be made for 230V, have a plug that works in most of the continent, and will have higher power.

I have occasionally needed an immersion heater in Europe, so when I passed an electrics shop in Germany once, I bought one. It was bigger and better made than the dime-store ones you get in the US. And because it was designed for 220 volts, it heats much faster than ours. I think it might even be unsafe in an ordinary coffee cup, rather than a mug, it's so big and sturdy.

I also wanted the (generic but trade name) grounded Shuco plug you get in Germany because it's so widely used and has so many adapters that I already own.

Just to give you an example of why you might need an immersion heater (I have a dual-voltage kettle as well), I have used in on a cruise ship to boil water for use in a sinus rinse bottle. (You might know the term Neti-Pot, a similar idea.)

I always travel with an immersion heater. In fact, I have two. I like a cup of coffee/tea when I get up and not all hotels have kettles in the room. (Although now I try to book hotels that have them.)

Whichever one you get, make sure it is dual voltage. I have ones made by Lewis & Clark and got them on Amazon.

I carry two because I burned one out in Venice and spent half a day trying to find one. No luck.

Heed the previous warnings about making sure the immersion heater is in water when plugged in. Otherwise, it becomes a paperweight. (One with a US plug is fine. Just use a european adapter. I use one of those sold by RS.) Because I am careful, my current one is over three years old.

It will boil the water in Europe in a few minutes. Yes, boil.