Diffusion of green utilization is a big challenge. A growing body of literature has suggested that governments play a core role in promotion of green utilization. The extant research of green utilization behavior is focused primarily on consumer preferences. So far, in-depth quantitative research of the government's role in the connection between green utilization and production is absent. Unlike previous research of green utilization behavior, this study established a dynamic adjustment mechanism for the government's subsidy policy for electric vehicles through the case study of Taiwan's electric motorcycle, so that the government's finite budget can be effectively allocated. Results indicate that emerging energy technologies reach the market competition conditions of economies of scale through government subsidy, subsidy policies should gradually phase out the market and transfer finite budgets to other emerging energy technologies that need to break through economies of scale. Therefore, the incentives phase-out mechanism of the electric motorcycle in this study will be helpful in the decision-making thinking of government and quantitative evaluation for the promotion of emerging energy technologies in the future.