My kitchen also a very mini size, there only have 2 feet width wall can install the 煤氣熱水爐, but the upper part is a windows, so the only way is install the 熱水爐 into the lower cabinet.
It not only keep the windows and upper cabinet, also can conseal the big size of 熱水爐 in the lower cabinet too. I never consider to install the 熱水爐 into bathroom because it is so ugly on the wall.