Grid Emissionality 2D: The REC Accounting Gap

Renewable Energy Certificates and Guarantees of Origin let a buyer claim "clean" electricity even though the grid delivers one shared mix of electrons to everyone. This simulator models the mechanism underneath that claim: real merit-order dispatch, where power plants are switched on cheapest-first until they meet demand, and the plant that clears the very last megawatt — the marginal plant — sets both the market price and the grid's true marginal emissions rate. Because wind and solar are dispatched first regardless of certificate ownership, buying a REC almost never changes which plant is marginal, exposing the gap between the emissions a buyer is allowed to claim avoided (grid-average accounting) and the emissions a REC purchase actually causes to be avoided (marginal/consequential accounting). A retirement toggle also demonstrates the double-counting risk that certificate registries exist to prevent. This 2D edition renders the same dispatch engine as a rotatable plant ring, a merit-order dispatch ladder, and a REC token flow lane instead of a 3D scene.