Interesting, does it just heat instantly on demand, or does it keep a small reservoir? How is the energy efficiency compared to a kettle?
Energy efficiency is about the same as a kettle - the tank is super insulated, and you only use what you need rather than boiling more in a kettle (and that then cooling down), that balances out the small tank losses. If you have solar it’s more friendly for that as it’s lower peak wattage so more likely to stay within your solar generation.
Here's another brand's innards of the reservoir: https://youtu.be/Q7TV73Y5kmo?t=614 . If I had to guess they keep it under high pressure so the water can be hotter than 100 deg C but still remain liquid.
I see several examples where the tap seems to be integrated into the sink or actually just another setting on the regular tap. That seems dangerous to me.