Heating water with an immersion heater and thermos flask

Today I will task about how we heat water in our Toyota or caravan with a relatively low power consumption.

For this, we use an immersion heater that has a nominal power consumption of 1000W. The water is inside a one liter steel thermos flask. Be careful of course not to fill it up too much to prevent the boiling water of sparkling out of the flask.

The water here has an initial temperature of 20°C (68F) and takes around 5 to 5 1/2 min to boil.

We successfully used the heater with different inverters. It also worked well on a relatively small model, like the Votronic 1200W and the 12V 200A Liontron battery without any issues.

There are even immersion heater models with lower power consumptions – often with a “portable” denomination. But of course it will then take accordingly longer to boil the water. But it might make sense if you have a smaller battery system or inverter. And there are DC models as well, that can be attached directly to a battery without an inverter at all.

But the main point for us was that this immersion heater just fits perfectly into the flask (after we removed the metal ring you can see on the picture). So after boiling, we can leave the water inside the flask without the need for an additional pot, and without having it to pour from one pot to the flask either.

The heater has a small plastic hook that it holds it in place. So it does not touch the bottom or any side of the flask.

After use the device is certainly hot, but it cools down quite quickly. If you use the water and empty the flask right away and do not have a proper surface on where to cool it, you can stick it back into the flask for cooling off.

And when not in use, the water heater takes nearly no space at all, or at least much less space than a normal electric water heater.

Two years ago, this water heater cost us roughly around 25 CHF. This is (today) around 25 EUR or 22 GBP. We got it from Galaxus, a swiss online shop. But we have no affiliation with it at all.

This model is called “Prosper Tauchsieder Real“, whatever this means. But as I said, there are plenty of different models out there.

Don’t forget to unplug the heater after use as it doesn’t have a sensor to detect when the water is boiling. The description however says, it has a dry detection feature. But I really never tried that out.

So this is it for today.