I got a 199,000 BTU tankless water heater, in addition to my furnace, and gas stove. I spent some time nerding over the numbers myself, and realized that I needed a bigger meter. I called Washington Gas, and once I got through to the right person, it was pretty easy. He did a similar calculation, and scheduled me to have a bigger meter put in – overall relatively painless, and it didn’t cost me anything.
That, and I love my hot water.