Carbon-based technologies continue to dominate the energy sector due to their high productivity and economies of scale. This creates an obligation for governments to provide incentives, such as taxes, subsidies and regulations, to encourage producers to implement cleaner technologies. We study a duopoly in which the incumbent is more efficient, has a higher propensity to invest and has a lower cost of capital. We derive the minimal subsidy (to the entrant) or tax (on the incumbent) sufficient to preserve the entrant in the market in the long run. The rate of the subsidy or tax depends on the underlying demand structure. The more differentiated the products and preferences of the consumers, the lower the subsidy or tax required to safeguard new entrants with innovative clean technologies.