Firstly, it doesn't matter how many energy certificates investors hold: they have no right to delivery, merely the right to present the certificates in payment for supply.

But in fact the redeemability of prepay certificates means that they are an excellent investment, because even if other investors are not prepared to buy at the unit market price, if the unit price falls below the physical market price, customers will buy them for redemption.

Think of an ETF with units returnable in the underlying: or a REIT with units returnable in payment for rent.

Secondly, I think we will see an energy clearing union wherein producers/issuers agree to accept each others' certificates in payment for supply, and then account with each other.

Such an energy clearing union would operate as a 'guarantee society' as a variation on a risk sharing P & I Club , managed by a service provider.

The first defence against over-issue is transparency - since sunlight is the best disinfectant, all energy clearing union issuance would be available for scrutiny.  Service providers like Thomas Miller would then act in accordance with agreed rules to manage issuance.

Finally, there is the point that certificates are returnable in payment at the location of the consumer, but issued by producers at different locations.

What this means is that it is necessary for a change in the distribution/utility business model away from intermediation.

But this is already happening, because to transform from an intermediary to a service provider is actually in the interests of the intermediary, because service provision is 'capital lite'.

That is precisely why banks got into the business of selling quasi-equity instruments such as index funds and ETFs to passive investors - it means the maret risk is with the unwitting investor, not them.

"The future is already here -- it's just not very evenly distributed" William Gibson