Dispatch Priority is the practice of giving certain power generators first preference when scheduling power supplies in a power system. It is typically applied to renewable power sources including solar and wind, where the fuel is free and where the cost structure of power projects is dominated by up-front, capital costs. Dispatch priority gives investors assurance that whenever the wind is blowing (or sun is shining), the energy generated by a project will be available for sale regardless of economic competitiveness, in turn generating revenue to pay back that initial investment. Without it, such power projects would be much riskier, and hence more expensive, to finance.
Where emissions targets are important, it is also sensible policy to give priority dispatch to those sources which generate electricity without emitting greenhouse or other polluting gases.