possible profit margins in an EROEI&lt;1 system. So no, your statement is not a correct representation of my post. And if any of those factors change - the input source is not inexhaustable, there are limits to production of the input source, and/or the profit margin disappears (declining demand for example), does the EROEI matter then? EROEI is irrelevant as a measure in any economic system I am familiar with. Admittedly, my economic experience is concentrated in oil and gas project economics, field economics, cost/supply calculations, proved reserves and such. Are there examples of EROEI being used in any other economic system as the primary criteria for green flagging a project? I can't say I have seen any presented around TOD, but certainly TOD does not define the known universe on the topic. What if your economic system changes because there are limits to those things you are used to being inexhaustable for energy invested? Either because of limits of production of the energy source (e.g. coal) you use for investment, or because of dramatic increases in demand for your source of your energy invested (e.g coal) from sectors of the economy that are switching (twitching) to coal because their former energy source (e.g. oil) is declining in availability, or became too expensive? I'm not trying to misrepresent your point. I'm asking if EROEI did not matter in the decade you worked because at that time there were no serious threats to the supply of energy invested. Does EROEI become