ᐅ District heating – domestic hot water via storage tank or instantaneous heater?

Hello everyone,

we are currently planning a complete renovation of a house (4-person household), including the installation work. The house has a district heating connection, which is currently used only for heating. In the two bathrooms, old, large electric instantaneous water heaters are installed.

We are now considering how to implement the new installation. Since everything will be opened up, installing new domestic hot water pipes is expected to be no problem.

I am not up to date on instantaneous water heaters, so here are my questions – maybe someone can help:

• Does it make sense to stick with instantaneous water heaters for the bathrooms? I see the advantage of having "more" water available for morning showers. However, the heaters should be compact and not an eyesore. Are there any other advantages to instantaneous water heaters?
• In the kitchen, I am considering a small instantaneous water heater under the sink. Advantage: I would get warm, drinkable water faster, for example, for cooking pasta. Does anyone have experience with this? I am especially interested in how quickly warm water arrives and whether it gets warm enough.

Thanks in advance!

Deraggi2 schrieb:

Does it make sense to stick with tankless water heaters for the bathrooms? I see the advantage that we have "more" water available for the morning shower. The heaters should be compact and not an eyesore. Are there any other benefits to tankless water heaters?

The price, space requirements, and speed. How would hot water from district heating be technically implemented, and what would it cost?

Deraggi2 schrieb:

In the kitchen, I’m considering a small tankless water heater under the sink. Advantage: I get hot, drinkable water faster, for example, for cooking pasta. Has anyone here had experience with this? I’m especially interested in how quickly hot water arrives and if it gets hot enough.

I heat my pasta water on the stove.
The mini tankless water heaters (3 or 3.5 kW) are only worth it for having a quick warm water flow for handwashing. The hot water only comes out as a small trickle. I currently have one myself. It’s perfectly enough for me. But washing large pots or similar doesn’t work with that. For that, you need a larger model (e.g., 9 kW) or one with a storage tank.

If you want to produce domestic hot water using district heating, you will need a different transfer station as well as a water storage tank, and you will probably have to adjust the tariff, which will cause ongoing (higher) fixed costs in addition to the consumption costs. This is a significant amount that initially has to be offset again by the "expensive" electricity.

Otherwise, if quick availability of hot water is important, you will still need a circulation line with a pump, which consumes both electricity and heat.

What benefits do you expect from using district heating for hot water compared to an instantaneous water heater?

K1300S schrieb:

If you want to heat domestic hot water via district heating, you’ll need a different transfer station and a water storage tank, and you’ll probably also have to adjust your tariff, which leads to ongoing (higher) base costs in addition to the consumption costs. That’s a significant amount, which initially has to be offset by the "expensive" electricity.

Otherwise, if fast availability of hot water is important, you’ll also need a circulation line with a pump, which consumes both electricity and heat.

What are you expecting from district-heated hot water compared to on-demand water heaters?

Thank you very much for your reply. Both options have their pros and cons, and I’m trying to work out the important aspects for myself.

Advantages of district heating:

- No on-demand water heaters needed in the bathrooms
- Sufficient hot water for four people if properly sized

Disadvantages:
- More expensive transfer station
- New piping must be installed
- Possibly not ideal for the kitchen due to risk of bacteria

Unclear: Costs for purchasing the station versus multiple on-demand water heaters, maintenance, etc.

Well, you can easily find the costs for the tankless water heaters yourself. Aunt Google will quickly provide the hardware prices. From about 250€ (approximately $275) for a branded unit. Multiply that by two and add a few more euros for the kitchen. Maintenance for both is almost negligible.

On the other hand, an estimated 3000+ EUR for a distribution station including domestic hot water preparation, plus around 1000 EUR more for the storage tank. Pipes, pump, small parts ... It all adds up.

Oh, and your district heating provider can calculate the ongoing costs for you.