biggest thing to understand with "thermal efficiency" with a woodstove is that you simply have to lose some in order to burn at all. think about stack temps, they come from the fire itself. without them not only would it be far and away harder to simply burn wood, the effects on chimneys is going to be pretty ugly. as for EPA, they aren't concerned with "thermal" efficiency, simply the amount of harmful particulates released into the air. the "btu's listed on the paper hang tag aren't even accurate to what you would attain with seasoned cord wood or a full load. its what is measured in the test itself with the cribs. as for the disparity with the test and real world, its simple, a stove which produces a lower GPH in the test should in theory produce a lower GPH in a real world situation. that doesn't mean all of them will simply due to different variables , but the majority will do so. as for the advancement of standards, its coming boys and girls, i expect the national requirements to at very least mimic washington state very soon, with tighter regs following. ESW is working hard to stay ahead of this as im sure my friend Fyrebug and his team are doing as well up there, its not easy, but its gonna get done.