Although recent studies have shown that electricity systems with shares of wind and solar above 80% can be affordable, economists have raised concerns about market integration. Correlated generation from variable renewable sources depresses market prices, which can cause wind and solar to cannibalize their own revenues and prevent them from covering their costs from the market. This cannibalization appears to set limits on the integration of wind and solar, and thus contradict studies that show that high shares are cost effective. Here we show from theory and with numerical examples how policies interact with prices, revenue and costs for renewable electricity systems. The decline in average revenue seen in some recent literature is due to an implicit policy assumption that technologies are forced into the system, whether it be with subsidies or quotas. If instead the driving policy is a carbon dioxide cap or tax, wind and solar shares can rise without cannibalising their own market revenue, even at penetrations of wind and solar above 80%. Policy is thus the primary factor driving lower market values; the variability of wind and solar is only a secondary factor that accelerates the decline if they are subsidised. The strong dependence of market value on the policy regime means that market value needs to be used with caution as a measure of market integration. Keywords: market value of variable renewables, renewable energy policy, CO 2 tax, feed-in-tariff, merit order effect, large-scale integration of renewable power generation
Highlights• Decreasing market value (MV) with wind and solar share is a result of policy choices • In long-term equilibria, wind and solar subsidies reduce MV, but CO 2 prices do not • Models with rising CO 2 prices see rising wind and solar (VRE) with no reduction in MV • Falling MV in models with VRE subsidy do not necessarily indicate integration problems • These results are confirmed using economic theory and in a power system model