Excellent really, nothing to do with a Redline I had 10 years ago. I didn't expect it to heat up so well! To the point that at maximum, it really burns (and it doesn't make sense). You need to set it to the degrees that satisfy you and only use the hot from the tap. If you mix, it unnecessarily burns electricity in case the hot is too hot for you. So you set it to the temperature that works for you and then just turn the hot all the way up on the mixer. And of course, like with all instant water heaters, use the water only when you need it and don't let it run unnecessarily.

Maybe not such a well-known brand, but in the field of water heaters, it is a "name". After purchasing one years ago and being very satisfied, friends and relatives who have also purchased it are also very satisfied. By far, it is the most economical solution for a water heater (for those who are still considering it), as long as you take into account: - reinforced power line and - incoming water temperature (very cold water will reduce the flow of hot water)

I have already bought two of them which I have been using for the last 3 years.
They don't make any noise when they are working.
I have them connected in series with the solar panel so that when there is no sun, they turn on automatically.

For those who say that it doesn't heat enough, they should check the settings to make sure they haven't set it to a limit.

It is an inverter and it draws as much power as needed to heat the water where you have set it.

It alerts you with a sound when you switch them to the hot water supply so that they don't get damaged (in case the solar panel has hot water).

It requires its own line from the panel.
A plumber doesn't need to connect it as it is very easy

I have had the device for 1 year.
The conclusions from the use are mixed.
The power economy is relative. If you take a bath like Cleopatra, you will cry.
If you take a quick shower, of course, you save.
So, the economy is relative.
If you consume the same amount of hot water as with a regular electric water heater, you are not saving. In fact, you are losing.
The cost should also include the electrician and the plumber. Both together, along with materials, cost about 180€.
Great attention is needed in the power supply. If the line cannot handle 8.2kw, then you start lowering it until the fuse can handle it. With a 20A fuse, it will work at 5.5Kw, so it will provide minimal water, resulting in not enough for a bath.
Also, a filter for salts at the inlet is necessary.
It does not make noise. Just a minimal humming that is covered by the sound of the falling water.
If I would buy it again? Probably not. It would be preferable to get a small solar one.

Very good. Beautiful and compact device.
If you are used to taking a shower with a water heater/solar panel, the reduced water flow might bother you a bit, as you need to compromise there. However, I think it's a habit (and it saves money!). Considering the advantages it offers, hot water whenever you need it, for as long as you need it (plus fresh...), it compensates for it.

I tried it during a relatively cold season when the cold water it takes is freezing, and I took a hot bath.

The only downside so far, which is also unacceptable, is a slight noise (like a DEI substation, with lower intensity of course but the same frequency) coming from the device (probably from the transformer, which might be of poor quality) in complete silence when it's on standby, and I have to turn it off occasionally from the panel and not have it permanently on.

Of course, this is relative. I have placed it centrally somewhere in the house, next to my office, so I can hear it and it bothers me, but someone who might be a bit hard of hearing or who will place it, for example, in the bathroom and close the door, won't have this problem, I think.

However, for some people, it might be annoying. I hope they see it and fix it.

UPDATE:
Unfortunately, in very cold temperatures (e.g. when it snows), when the incoming water is much colder, it cannot cope. The flow needs to be so low in order to heat it to 42/43 degrees that it becomes impossible to take a bath.
However, I believe this is not specific to this device itself. It mainly has to do with this "technology" in general, where in order to be covered, you need at least 12 kW.
In other words, three-phase power...

I have it for 5 days now. Beautiful machine, very easy to connect and use. Its screen is bright and readable. The three touch buttons +, --, and power on off, you barely touch them.
The machine is really powerful and fast in adjusting the temperature you ask for. Silent and immediate. It does exactly what it says in the technical specifications and more.
Connection with a 6mm cable and a 35A - 40A fuse is necessary.
Unfortunately, the excellent machine is overshadowed by the very poor quality phone - shower that accompanies it, which is a disaster.
While the machine can provide more water output, the phone - shower cannot withstand it and breaks - comes apart. So you will need a screwdriver to repair it and continue showering.
For this reason - jokingly - one star is deducted as the main machine is a true BEAST of power. I hope the company will replace it soon with a similar one to the capabilities of the main unit.

It was purchased about 5 months ago. It was installed as the main unit in the bathroom (sink & bathtub used only for showers), with complete plumbing (flow regulator, thermostat valve, bypass) and electrical installation (new line from the single-phase panel), in a 1st floor 7-storey apartment building, in a series with solar panels. It works perfectly, has very readable indicators, remembers the settings, and overall "you install it, adjust it, and relax". For the first time in years, morning showers and hand washing can be done with hot water, as before, during winter, it was not easy to decide to use hot water from the solar panels, even if it was available. It is essential for washing our baby as well. You will enjoy a small luxury in your everyday life and save water and electricity. I note that you will need to make a small compromise regarding the shower supply.

I would like to add, after about a year and a half of use (August 2018), that my above evaluation still stands. I highly recommend it, as long as you accept the aforementioned compromise for the shower supply during winter. Additionally, I emphasize that it is highly worth installing the recommended thermostatic valve at the inlet, for safety reasons as well as for comfort in use, despite sounding like a scientific fantasy for Greek standards.