Cost of instantaneous water heater and infrared heater

Hello everyone,

I am hoping for your help and experiences. I have bought an apartment as a capital investment and it needs to be completely renovated. It is a 3-room apartment in Stuttgart with 71 sqm. Currently, there are gas individual stoves in 2 of the 3 rooms and a gas boiler for hot water in the bathroom.

I plan to equip the apartment with infrared heaters in all rooms and remove the gas individual stoves. 1. Because it would be very expensive to install a gas boiler since I would also have to install a complete central heating system, meaning radiators with pipes everywhere, etc., and 2. You can hardly find anyone who can do it anytime soon. Waiting time is several months.

Now, however, I have the problem with the hot water. The bathroom will also be completely renovated and redesigned, the bathtub will be removed and a walk-in shower will be installed. For this, the gas boiler has to be moved a few meters. The same problem here, it is very difficult to find someone who will do it, since the gas pipes have to be moved, which only a professional can do. I think that would also cost a few thousand. Now I am considering whether it might make sense to install an electric instantaneous water heater and get rid of everything to do with gas. This would also have the advantage of no maintenance costs and no chimney sweep costs. However, you find very contradictory opinions about the operating costs of an instantaneous water heater, ranging from unaffordable to not so bad.

Are there people here who have experience with an electric instantaneous water heater regarding the costs? I would be very grateful for any experience. I plan to rent the apartment to a shared flat later, and students often do not pay much attention. Of course, I can pass on the costs, but if they are very high, they might move out quite quickly and I would have a constant turnover, which I do not want. So now I have written a lot, I hope someone can share some experiences here :)

Regards

Darius

We have installed a hot water heat pump and are satisfied with it. Nevertheless, next time I would actually install an electric instantaneous water heater, but I would take a closer look at it first. As long as it works the same way as with gas, that would be my choice.
For us, the boiler actually constantly heats the water, even though we often don't need it. Don't worry, we do shower, but we are often away or only two of us anyway, so I believe an instantaneous water heater would be significantly cheaper, just because of the initial cost.
Now electricity compared to petrol and gas has, I believe, become significantly cheaper again, and as you say, there are no problems with installation or costly maintenance.
If I were in your place, I would seriously consider it, also because it is simply feasible for you.
If someone cannot handle energy consumption, then someone won't be able to handle gas, electric, and a heat pump either.

Now I am wondering whether it makes sense to install an electric instantaneous water heater and abolish everything related to gas. It would also have the advantage of no maintenance costs and no chimney sweep costs.

However, the effort is considerable. - Is the house connection designed for this? - Is the apartment connection designed for this? - Chasing walls and laying cables - Installing an instantaneous water heater with 18-24kW - Waiting weeks or months for craftsmen ==> Costs? If everything has to be done, for example because the house connection does not provide such power, then it will be really expensive. Operating costs: small 18kW instantaneous water heater for 10 minutes daily = 1,100 kWh per year = €300 electricity costs P.S. Are you also the owner of the entire house? Otherwise, you need the approval of the owners' association for almost everything.

But the effort is considerable.
- Is the house connection designed for it?
- Is the apartment connection designed for it?
- Chiseling walls and laying cables
- Installing a DLE with 18-24kW
- Waiting weeks or months for craftsmen
==> Costs? If everything has to be done because, for example, the house connection does not provide such power, then it will get really expensive.

Operating costs: smaller 18kW DLE for 10 minutes daily = 1,100 kWh per year = €300 electricity costs

P.S. Are you also the owner of the entire house? Otherwise, you need the approval of the homeowners' association for almost everything.

Thanks for your answer.
- According to the electrician, the connection is okay (evaluated based on the picture sent, will of course still be checked on-site, hopefully it stays "okay," otherwise the DLE plan is off).
- The entire electrical system will also be redone, so chiseling walls is necessary anyway, also for the infrared heaters.
- I have craftsmen for everything except gas, so no waiting in this case.

Your example calculation is also circulating on the internet, hence my concerns. But by now, I rather think it’s a simplistic calculation because for a household of three people you would then expect €900 in electricity costs, which nobody with a DLE could confirm.
Do you have a DLE yourself or is this also a calculation from the internet?
I think one mistake in the calculation is that it assumes the DLE runs continuously for the 10 minutes you shower, which I don't think is the case, or at least not at full power; nobody showers with the hot water turned fully up.
But how much less it is, that’s the question.
Therefore, I’m asking more from people who have practical experience and less from calculated values, unless more parameters are included, but I think that would be a complicated calculation with "how much energy is needed to heat 1 liter of water from 8 to 25 degrees," etc...

We installed a hot water heat pump and are satisfied with it. Nevertheless, next time I would actually install an electric tankless water heater, but I would take a closer look at it beforehand. If they work the same way as with gas, that would be my choice. For us, the boiler actually constantly heats the water, even though we often don't need it. Don't worry, we do shower as well, but we are often away or only two of us, so I believe a tankless water heater would be significantly cheaper, just because of the purchase cost alone. Now, I think electricity has become significantly cheaper compared to gasoline and gas, and as you say, there are no problems with installation or costly maintenance. I would seriously consider that if I were you, also because it’s simply doable for you. If someone can’t handle energy consumption, then anyone can’t handle gas, electric, and a heat pump either.

Thanks for your experience, can you say how much the hot water costs you per month or is it not separated in the meter between hot water and heating?

Your example calculation is also circulating on the internet, that's why I have concerns.

This is roughly self-calculated. But it matches what’s on the internet.
You can always calculate yourself. Simple math.

Do you have an instantaneous water heater (DLE) or is that also the calculation from the internet?

I myself have also had an apartment with an instantaneous water heater. But you will never find anyone who has a separate meter for the instantaneous water heater. That is the only way to determine exact consumption. And that then has to be adjusted with a 300% deviation, as every person and every family is different (number of people, duration of shower, number of showers, hot water in kitchen, bathtub vs. shower, etc.)
I would have estimated my costs there—as a single person not showering daily because of sports and other reasons—at 200-250€.

I think one mistake in the calculation is that it assumes the instantaneous water heater runs continuously for the 10 minutes you shower, and I think it doesn’t, or not at full power, no one showers with the water fully turned to hot.

I don’t turn off the water when I shower, and many people don’t either. And I also don’t shower with cold water. And you need hot water in the kitchen as well.

But how much less it is, is exactly the question.

Yep.

Therefore the question is more for people who have practical experience with this and less with calculated values, unless more parameters are included, but I think that would be a complicated calculation with “how much energy is needed to heat 1l of water from 8 to 25 degrees” etc...

Yes, it is that complicated (and simple at the same time), but the user plays a big role. But you can practically ask anyone who produces hot water and inquire about their energy consumption.
With my heat pump, a COP of 4 (simpler to calculate), I have consumed roughly 1,800 kWh of "heating energy" for hot water preparation (so electricity x 4). If you used the instantaneous water heater, (it would be comparable), you would be at 540€ electricity costs (at 30 cents per kWh). But people also shower more often because my kids sometimes stand under the shower when they are with me...
With my electricity contract and thanks to the heat pump, it’s only 110€. Just for comparison. So the very first calculation at the top fits quite well.

Your example calculation is also circulating on the internet, that's why I have concerns.

Closing remark: no concerns, hot water with instantaneous water heaters is an expensive pleasure with frequent use. But not necessarily more expensive than gas.