All of my hot water heaters (the small wall units) when I lived in Japan used propane gas (well, LPG which I assumed was usually propane). Are you sure your hot water heater uses NG/methane?

Nevertheless, this event demonstrates again how vulnerable Japan is, given that it imports nearly all of its energy sources, with a great share coming from the ME. Anything that happens in the ME thus is of interest to the Japanese, which explains why during Abe's recent tour of that area he was accompanied by a small army of Japanese corp. executives, a first.

I'm pretty sure its LNG. I'll have to check my gas bill when I get home now.

But I see a lot of houses with LPG cylinders outside them as well.