ᐅ Comparison of Different Heating Systems

KarstenausNRW schrieb:

- And finally, we’re talking about increasing the temperature for the legionella control program from 50 degrees (normal hot water temperature) to 60 degrees.
This means the water temperature needs to be raised by 10 degrees once a week. With a typical 3 kW heating element, we’re looking at weekly costs of about 50 cents.

However, the legionella control program requires a temperature of 70 degrees, as you would know if you had skimmed through the linked document.
Anyway, when a 3 kW heating element runs, those 50 cents are consumed in about 20 minutes.

Nutshell schrieb:

However, the legionella program needs to be set to 70 degrees, you would know that if you had skimmed through the linked document.

No, legionella bacteria die at 60 degrees.
70 degrees is often recommended just to have a safety margin and to ensure that 60 degrees is reached in the pipes and at the taps.
In a single-family house, this is usually not necessary because the pipes are sufficiently flushed.

Nutshell schrieb:

Anyway, when a 3 kW heating element starts running, the 50 cents are used up after 20 minutes.

Currently, 1 kWh costs 30 cents, not 50 cents.
Ideally, this is done with solar panels, which means the cost is the lost feed-in tariff of about 8 cents.

But otherwise, yes, and? Even if it runs once a month or week, it still won’t come close to hundreds of euros.

Nutshell schrieb:

However, the legionella program must reach 70 degrees, as you would know if you had skimmed the linked document.
Anyway, when a 3 kW heating element starts, the 50 cents are spent after 20 minutes.

You don’t want to understand. With a constant temperature of 50°C (122°F), a legionella program at 60°C (140°F), and regular water usage, you don’t need 70°C (158°F). In that case, you simply don’t have any legionella that need to be killed. Otherwise, they die at 55–60°C (131–140°F), and at 70°C (158°F) you are 100% safe.

And yes, you only need about 20 minutes. The heating element doesn’t require longer to raise the temperature from 50 to 60°C (122 to 140°F). And if it’s 30 minutes at a 35-cent electricity price, it still costs less than 50 cents (photovoltaics are cheaper).

From a scientific study (RKI) – legionella prefer cool to warm water in stagnant and decaying pipes; they dislike very warm, flowing water:

Everyone is welcome to have their 60, 80, 100, or even 150 degrees Celsius (140, 176, 212, or even 302 degrees Fahrenheit) supply temperature with the corresponding pressure. Like having their own nuclear reactor in the basement. Currently, uranium is just easy to get in Niger, so why not just take a school trip and put together a nice system.

Seriously now: Nutshell, you want a system that operates miles beyond any kind of normal standards. You’re free to do so, but for that, you don’t ask a professional for advice.

Nutshell schrieb:

Well, when I go on vacation, I prefer to keep it at 60 degrees.

No water is used during vacation, so the pipes will reach room temperature. According to your own statement, there is no risk at 20 degrees. Therefore, I would rather turn off the hot water supply (there are now options to switch it back on before returning, either with a timer or via the internet). Then you set it once to 70 degrees and run hot water everywhere for 5 minutes upon return. I wouldn’t think of keeping hot water at 60 degrees for 3 weeks...

How much does it actually cost per year, in euros, to heat a KfW55 house of around 130 m² (1,400 sq ft) plus provide hot water using an air-to-water heat pump with underfloor heating? Not estimated, but actual costs.