Minitank Water Heater
About
Instead of heating a large quantity of water, a minitank heater heats a small amount. Thus, it is capable of higher efficiency (less heating loss) compared to a full tank water heater. Its advantage for off-grid use (assuming limited electrical power) lies in using a small heater element - unlike tankless heaters (on-demand heaters) - which require much more power (4-8kW) compared to minitank (1-2 kW). Disadvantage is that you run out of hot water if you use up more than the tank - say a long shower.
From a critical perspective - it is about 1.5 kW - worst of 2 worlds - don't have enough continuous hot water, and waste energy. You can tell by their larger size than true tankless.
Bosch
Email to Bosch Customer Support
I have the Tronic 3000T ES-8 minitank heater. It says it uses 1440W at 120V in the specifications (https://www.bosch-thermotechnology.us/us/media/country_pool/documents/downloads-for-bosch-products/point-of-use-mini-tanks-manuals/6720801072_tronic3000t_es2.5-4-8_iom_en_sp_07.2022-2.pdf) but the installation calls for 12 ga/ 20A breaker. According to the NEC 80% rule, the power specification should be met with 14 ga wire and a 15A breaker, given that 125% of 12A is exactly 15A. Is there a reason that you are specifying an upsize breaker? You mention specifically in the installation that your breaker size is 'according to the NEC' - but according to the NEC 125% rule, this should really be 15A, not 20A, biach.
