I have the Dafi 5.5kW for 6 months, I am quite satisfied. Although it had a leakage problem at the beginning at the connection of the brass piece with the plastic (P). I thought it was glued and requested a return, (the screwdriver accepted it, no complaints). That's why 1 star less. It was properly screwed, and the -red- sealing ring had cracked probably due to excessive tightening. I replaced it with a rubber one and the problem was solved.
The 5.5kW is excessive for me for household dishwashing, especially in the summer it makes it very hot and requires a lot of cold for mixing, resulting in a large water flow and splashing, since you cannot adjust the temperature in this type of water heaters.
Overall, it's worth the money!!!

I put it in the attic. It was easy to install. I can’t hear it because it’s in the attic. For a shower it’s fine. Obviously it’s not for filling a bathtub; I’m talking about the 7.3 kW model. At this price, it’s perfectly fine. It is Swedish. It is still being tested; I’ll come back with new updates in a little while because with 2–3 uses at the beginning everything seems perfect.
An electrician was needed because it requires its own fuse and wiring.

I rarely get around to writing a detailed review, but since no one else has written about this product and, overall, I was satisfied, I will do it. At first glance it doesn’t inspire confidence: the very small size, the plastic clamps, and the fact that it’s made in Poland make you wonder, “Will this thing work?” Well, it does, and very well at that. Since I can’t install a solar water heater in my house and I wanted hot water immediately, I chose the instant water heater solution, knowing the issues these devices can have. To start with, I decided to go with the small instant water heater category, with the intention of moving to a larger one if it didn’t meet my needs. I chose 7.3 kW because 5.5 kW is only just enough for a shower. The goal was to have lukewarm water immediately during the warmer months without having to turn on the conventional water heater. For the cold months, I don’t expect this machine to cover my needs; however, time will tell what it can do in the future. I’ve connected it in parallel with the conventional water heater, and if it struggles I’ll use it in a “hybrid” way by turning on the conventional one first for a while, or I won’t use it at all. It should be noted that because it draws a lot of power, close to 30A, care is needed with the electrical connection. I connected it to the main hot-water supply, although this is not recommended, first because there is heat loss due to the pipe run and second because of the pressure drop it causes (since the water inlet/outlet is of small diameter). Despite all the difficulties, it manages, and I have hot water immediately throughout the house. At the tap’s hottest setting, that is, at the highest possible pressure, which is relatively low but still lets you shower easily, especially if you also use a high-pressure shower head, it delivers very hot water in seconds, of course depending on the distance of the tap from the machine. The water goes from 23 to 46 degrees measured and stays stable there without fluctuations in performance. Personally, for showering in the summer it is very hot and I have to mix it with cold water, so the pressure also increases because of the mixing and I shower very comfortably. The only problem is that at first it takes some getting used to: if the water is hot and you want to cool it down, you turn the tap toward cold, but if you overdo it, after a certain point its pressure sensor no longer detects that you are drawing hot water, so the instant heater shuts off (you can also hear the characteristic click from the machine) and only cold water comes out, so you need to find the point where this happens. So far I am very satisfied; it does what it says and has fully met my needs. Of course, I don’t have tremendous demands, but for the money and its kW rating it is excellent, which is why I gave it 5 stars. It is noticeably cheaper than the competition, and to move to another product at 9 kW+ you have to spend twice as much. Someone who is more demanding should go for something more powerful and more expensive. I still need to see what it will do in winter and whether it will prove reliable over time, although even if only the second part turns out to be true, that will be enough for me.

Update: in winter, the 7.3 kW turned out to be marginal after all; I wanted the water hotter, so I changed the heating element and installed the 2-phase 11 kW one. The water was now satisfactory, but when it warmed up again it was excessively hot and I couldn’t adjust it to the desired temperature by mixing because when I turned it toward cold, at some point the Dafi shut off and it became completely cold. Perhaps the ideal would have been 9 kW. Also, something else very important: DO NOT CONNECT IT AFTER THE CONVENTIONAL WATER HEATER. What I mentioned above as hybrid operation is a complete failure. Once I forgot and left the conventional water heater on for longer, so the water was already hot, then it passed through the Dafi and got even hotter, which caused the Dafi’s plastic fittings to melt and the pipe to burst out, and I ended up covered in water! Luckily I was there and shut the water off immediately, so I didn’t flood the place!