"But I can't think of anywhere where it's the only solution."

Have you thought of the planet Earth? That's what we're talking about, isn't it?

Largely, of course, the developing world can't leap to nuclear, but nor is there value in RE long-term, cost-wise or in mitigating AGW, as real experience teaches us. Hydrocarbons, in most cases, are the affordable pathway to the state of civilization to which is aspired, seguing into urbanization and nuclear. The developed world can head nuclear now, or hydro where EROIE viability and environment permits.

Whatever, enough of me chasing tripe-peddling dreamers through warrens. Either we sober-up and act logically or allow AGW to gallop away.

Aiden, I think I see the point you are making;
The energy required to be sold to pay the bill does in fact add to the
energy that the buyer needs for his business anyway.

The point of eroei is to measure the viability of the process.
If eroei = 7 and overheads reduce the viability eroei to 7-2 can it
function with an overall eroei of 5 ?

If it cannot then it fails because the eroei was not high enough and
cannot support itself.

I suspect that this is the reason solar and wind can never build the
next energy regime without coal.

So there are two ways of looking at this problem as above.
It is only a factor with plant with a marginal eroei to start with.

It is not a factor with coal because it has an eroei, from what I have read of 30.
Oil is becoming marginal because its eroei seems to be around 10.
This seems a likely figure as the major oil companies are having
financial difficulties with their return on investment in search & development.

Luciferase, I have thought of the planet Earth, but it receives an enormous amount of energy from the sun, and IIRC a previous study has found that (100km)^2 of solar panels would be enough to meet the entire planet's electricity needs.

If there's anywhere where nuclear is the only alternative to fossil fuels, it's likely to be a small densely populated island.

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Bazz, the point of eroei is to measure the TECHNICAL viability of the process, not the commercial viability. If something fails commercially it's probably because the costs are too high. EROEI is one of the factors that influences those costs, but rarely is it the main factor.

In the early days EROEI was very important because energy returns were low and the energy invested was high; often higher than the return, and everyone knew it wouldn't be much use for on grid applications until that was addressed. But we're long past that stage now. EROEI measurements can still be of some use for checking the environmental credentials of renewable energy infrastructure are as claimed, but some people seem intent on assigning it a much greater significance. I still struggle to comprehend how otherwise intelligent people can believe the absurd proposition that an advanced society needs an EROEI of at least 7.

Oil is becoming marginal not because of EROEI but because oil prices have fallen. And nuclear isn't always a financial success despite its very high EROEI.