Merit order
Merit order is a foundational principle in competitive electricity markets for dispatching generation resources, ranking available power plants by their ascending short-run marginal costs and activating them sequentially from lowest to highest until demand is met, thereby minimizing the total cost of electricity production.[1][2] This approach constructs an aggregate supply curve by stacking generator bids or offers, ensuring that low-cost units—often nuclear, hydroelectric, or renewables with near-zero variable costs—are prioritized over higher-cost fossil fuel plants.[3][4] The merit order mechanism determines wholesale electricity prices through uniform pricing, where all dispatched generators receive the clearing price set by the marginal (highest-cost) unit required to balance supply and demand in real time.[1] This incentivizes generators to bid close to their true marginal costs, fostering efficiency in markets like those in Europe, Australia, and parts of the United States, though deviations can occur due to transmission constraints or ancillary service requirements.[2] A key implication is the merit order effect, whereby additions of low-marginal-cost capacity, such as intermittent renewables, shift the supply curve rightward, displacing costlier thermal plants and exerting downward pressure on prices during high renewable output periods.[5] This dynamic has driven observed price reductions in markets with rising wind and solar penetration, underscoring the protocol's role in integrating variable generation while highlighting challenges for conventional plants' revenue adequacy.[6] ![German electricity production mid-December 2017 from BNetzA SMARD portal][center]This illustrative snapshot from Germany's market reveals merit order in practice, with renewables dominating low-cost dispatch amid variable demand.[7]