ᐅ Towel Radiators for Bathrooms – Electric or Connected to the Heating System?

Hello everyone,

I’m starting my forum membership with a quick question:

We are building a KfW70 house with underfloor heating. In the bathroom on the upper floor, which is about 13sqm (140 sq ft), we want to install an additional towel radiator to dry towels and to quickly warm the bathroom during transitional seasons. It would only be in use for a few minutes up to an hour per day, and only on cool days. We have been offered two options: an electric towel radiator and one heated by the hot water system. Which option is recommended in terms of cost and effectiveness?

My (non-expert) thoughts so far are: For the electric one, it would probably be a 600-watt device, which seems quite high in electricity consumption. The hot water option, on the other hand, is supplied at about 60-65°C (140-149°F), but it would draw from the 300-liter (79 gallon) storage tank used for showers and baths, so I’m concerned there might be shortages quickly in a three-person household. Or is that unrealistic?

I would be very grateful for any advice.

I believe there is a misunderstanding. Your radiator will definitely not be supplied by your drinking water.

When warm water is mentioned here, it refers to your heating circuit, which, however, does not provide enough supply temperature as designed. This will just end up as an expensive towel rail. Nothing more.

An electric heating cartridge makes sense; the power consumption is negligible considering the usage time.

In bathrooms, floor heating usually requires cutouts around the bathtub and shower areas to achieve the room temperatures assumed in the heating load calculation. This is the case even with the smallest floor heating pipe spacing.

It was referring to the drinking water. As mentioned, it has a higher supply temperature. However, I couldn’t find any information about this online either.

In our case, the builder installed towel radiators precisely because of the described issue. They operate on the same loop as the underfloor heating, meaning they use a low flow temperature, but they have a large surface area. Whether they will be effective, we will only find out after the winter.

We will probably not need them at all, as the underfloor heating alone should be sufficient, but it was a matter of the calculations. According to those, the required room temperature theoretically could not be reached with underfloor heating alone.

If needed, the radiators can also be retrofitted with an electric heating cartridge. Power outlets for this are also planned on site.

@ClaasC.
If it was really the domestic water, I could only imagine it like this:
Instead of a dedicated domestic hot water storage tank, you would use a combined storage tank, and the coils inside the combined tank would serve as a second heating circuit exclusively for the towel radiators.
THAT makes sense. Although this means that a completely separate heating system needs to be balanced on the pressure side (expansion vessel, valves, etc.) and the storage tank becomes more complex.
For the few hours of operation per year, I would definitely recommend the heating cartridge.
At the very least, make sure to provide a separate dedicated electrical outlet within reach!

ClaasCPunkt schrieb:
It was about the drinking water. Since, as mentioned, it has a higher supply temperature. But I couldn’t find any information about it online.

Hello.

If you want to use the drinking water for your heating system, you face several problems:
(1) You won’t be able to reuse the water – or do you want to drink water that has circulated through a dirty radiator? So you would be discharging the water from the radiator directly into the drain...
(2) You will need a new radiator every 2 years because it will corrode much faster than you can imagine.

If your builder really suggested this to you, you should try to end the cooperation as soon as possible...

@Häuslebauer40:
If your radiator is connected to the house heating circuit, you unfortunately cannot retrofit an electric heating rod...
How do you expect to prevent the water from flowing back into the heating circuit instead of staying inside the radiator?
With the heating rod, you would be heating your entire heating system...
Effectiveness ~0. Cost = huge!

@ClaasCPunkt:
At 600 watts and 1 hour per day, assuming electricity costs of 20 cents per kWh: 0.6 kW * 1 h * 0.20 Euro = 0.12 Euro per day.

Best regards,
Micha