[ars]

Is there a reason you are ignoring transmission and generation losses?

By your standard natural gas is also 100% thermodynamically efficient - all of it ends up as heat. Some of it outdoors, sure, but that is true for electric heat as well. Those thin electric lines outside your house get pretty hot.

[sbierwagen]

Is there a reason you are ignoring transmission and generation losses for natural gas? Methane isn't a frictionless fluid, it costs real money to pump it through pipelines. And, of course, you have to dig it out of the ground in the first place.