Nemet's analysis does not invalidate the policy prescription based on deployment-led cost reductions which is included in IEA ETP projections to 2050. The projections are also based on analyses of the cost reduction potentials to be mobilised in future learning phases, and milestones towards competitiveness in progressively broader electricity markets (see IEA Technology Roadmaps, in particular IEA, 2010c). Resource exhaustion - when good sites get more scarce or remote, or if the proportion of variable sources in electric generation pushes up integration costs - can slow deployment and progress along the learning curve, but would not modify its slope.