[mech987]

Isn't heating a really good way to use natural gas compared to other ways to use it? 90%+ efficiency ain't bad.

[pfdietz]

That's actually poor efficiency, since there's a large second law loss burning the natural gas to make low grade heat.

You can get COP > 100% with a gas-fired heat pump, which are used commercially and in some larger (> 4000 sq. ft.) homes.