ᐅ Costs of tankless water heaters and infrared heating systems

Hello everyone,

I’m hoping for your help and experience.
I bought an apartment as an investment, and it needs a complete renovation.
It is a 3-room apartment in Stuttgart with 71 sqm (765 sq ft).
Currently, two of the three rooms have individual gas stoves, and there is a gas water heater in the bathroom for hot water.

I plan to install infrared heaters in all rooms and remove the individual gas 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 with radiators and piping throughout the apartment, and
2. It’s almost impossible to find someone who can do it anytime soon, with waiting times of several months.

Now, I have a problem with hot water. The bathroom is also being completely renovated and redesigned; the bathtub will be removed and replaced with a walk-in shower. Because of this, the gas boiler needs to be moved a few meters.
Here the same problem arises — it’s very difficult to find a professional who can do this, as moving gas lines must be done by a specialist.
I imagine this could also cost several thousand euros.

Now I’m considering whether it might make sense to install an electric tankless water heater and do away with all gas-related equipment. This would also have the advantage of no maintenance costs and no chimney sweeping costs.
However, there are very contradictory opinions about the operating costs of an electric tankless water heater — some say it’s unaffordable, others say it’s not that bad.

Are there people here who have experience with electric tankless water heaters regarding costs? I would be very grateful for any insights.
I plan to rent the apartment to a shared flat in the future, and students often don’t pay much attention to such things. Of course, I can pass on the costs, but if they turn out to be very high, tenants might move out quickly, causing a constant turnover, which is not what I want.

Well, I wrote quite a bit — I hope someone can share some experiences here 🙂

Best regards

Darius

We installed a heat pump for domestic hot water and are satisfied with it. However, next time I would actually consider installing an electric tankless water heater, but I would take a closer look at them first. If they work the same way as gas-powered ones, that would be my choice.

In our case, the boiler continuously heats the water, even when we often don’t need it. Don’t worry, we do shower regularly, but we are frequently away or only two people living here, so I believe a tankless water heater would be significantly cheaper, just based on the initial cost.

Now, compared to gasoline and gas, electricity seems to have become much cheaper again, and as you said, there are no issues with installation or costly maintenance.

If I were you, I would seriously consider this option, especially since it’s easy for you to implement.

If someone can’t manage energy consumption, they won’t be able to handle gas, electric, or a heat pump either.

Dariusbau schrieb:

Now I am considering whether it makes sense to install an electric tankless water heater and completely do away with anything gas-related. This would also have the advantage of no maintenance costs and no chimney sweep fees.

However, the effort involved is considerable.
- Is the main electrical connection designed for this?
- Is the apartment’s electrical connection adequate?
- Chasing walls and laying cables
- Installing a tankless water heater with 18–24 kW
- Waiting weeks or months for craftsmen
==> Costs? If everything has to be done, for example if the main connection cannot supply such power, it will get really expensive.

Operating costs: smaller than 18 kW tankless heater for 10 minutes daily = 1,100 kWh per year = $300 electricity costs

P.S. Are you also the sole owner of the entire building? Otherwise, you will need approval from the homeowners’ association for nearly everything.

nordanney schrieb:

However, the effort involved is significant.
- Is the main utility connection designed for this?
- Is the apartment connection designed for this?
- Chasing walls and installing cables
- Installing an instantaneous water heater (DHW heater) with 18–24 kW
- Waiting weeks or even months for contractors
==> Costs? If everything needs to be done because, for example, the main connection does not provide that capacity, it can get really expensive.

Operating costs: small 18 kW instantaneous water heater running 10 minutes daily = 1,100 kWh per year = $300 electricity costs

P.S. Are you also the owner of the entire building? Otherwise, you will need approval from the homeowners’ association for almost everything.

Thanks for your reply.
- According to the electrician, the connection is fine (based on the picture I sent, it will of course be checked on site later—I hope it stays “okay,” otherwise the instantaneous water heater option is off the table).
- The entire electrical system will be redone anyway, so chasing walls is necessary regardless, also for the infrared heaters.
- I already have contractors for everything except gas, so no waiting in that case.

Your example calculation is also circulated online, hence my concerns. But by now, I tend to think it’s a rough estimate since for a household of three, that would mean about $900 in electricity costs, which no one I know with such a heater could confirm.
Do you have an instantaneous water heater yourself, or are you quoting the same online calculation?
I think one error in the calculation is assuming the heater runs at full power for the entire 10 minutes of showering. It probably doesn’t, or not at full capacity—no one showers with the water set to maximum hot.
But exactly how much less is the question.
That’s why I’m more interested in practical experience from people, rather than just calculated values—unless more variables are considered, but that would be a complex calculation involving “how much energy is needed to heat 1 liter of water from 8 to 25 degrees Celsius (46 to 77 degrees Fahrenheit)” and so forth...

Arauki11 schrieb:

We installed a hot water heat pump and are satisfied with it. However, next time I would actually consider installing an electric instantaneous water heater, but I would want to take a closer look at it first. If it works the same way as with gas, that would be my choice.
In our case, the boiler constantly heats the water, even when we often don’t need it. Don’t worry, we do shower regularly, but we are often away or only two people living here, so I believe an instantaneous water heater would be much cheaper just based on the initial investment.
Now, electricity has become significantly cheaper compared to gasoline and gas, and as you said, there are no issues with installation or costly maintenance.
If I were you, I would seriously consider it, also because it is easy for you to implement.
Anyone who can’t handle energy consumption won’t do better with gas, electric, or a heat pump anyway.

Thanks for sharing your experience. Could you say how much the hot water costs you per month, or is it not separately metered between hot water and heating?

Dariusbau schrieb:

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

That’s roughly calculated by myself. But it matches what’s found online.
You can always calculate it yourself. It’s basic math.

Dariusbau schrieb:

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

I have personally lived in an apartment with an instantaneous water heater as well. But you will hardly find anyone who has a separate meter for the instantaneous water heater. That’s the only way to determine exact consumption. And even then, you have to apply a 300% variance because every person and every family is different (number of people, duration of showers, number of showers, hot water use in the kitchen, bathtub vs. shower, etc.).
I would have estimated my costs—since I don’t shower daily due to sports and other reasons—as a single person at around 200–250€ (about 220–275 dollars).

Dariusbau schrieb:

I think one mistake in the calculation is assuming that the instantaneous water heater runs nonstop during the 10 minutes you shower, but I believe it doesn’t run constantly or at full power; nobody showers with the water turned fully hot.

I don’t turn off the water while showering, and many people don’t. I also don’t do cold showers. Plus, you need hot water in the kitchen too.

Dariusbau schrieb:

But how much less it actually is—that’s the question.

Yep.

Dariusbau schrieb:

That’s why I’m asking people with practical experience rather than just calculated values, unless the calculation involves more parameters, but I guess that would make for a complicated (energy) calculation like ‘how much energy is needed to heat 1 liter of water from 8 to 25 degrees’ and so on…

Yes, it is complicated (and simple at the same time), but the user really makes a big difference. You can practically ask anyone who heats water about their actual energy consumption.
With my heat pump with a COP of 4 (makes it easier to calculate), I’ve used roughly 1,800 kWh (kilowatt-hours) of “heating energy” for hot water production (meaning electricity consumed times 4). If you used an instantaneous water heater with the same consumption, you’d be looking at about €540 (around $590) in electricity costs (assuming 30 cents per kWh). But in my household, there tends to be more frequent showering since my kids sometimes shower when they visit.
Thanks to my electricity contract and the heat pump, it only costs me about €110 (around $120). Just to give a comparison. So the initial calculation at the very top is quite accurate.

Dariusbau schrieb:

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

Final note: no worries—the cost of hot water with an instantaneous water heater is expensive with frequent use, but not necessarily more expensive than gas.