First, we want to assess whether such a global subsidy would be of an order of magnitude compatible with the current and envisioned financial flows going from developed to developing countries such as Official Development Aid (ODA), and figures put forward in the discussions under UNFCCC. Perhaps as importantly, we try to critically highlight the various steps needed to arrive at a final subsidy cost for a global feed-in tariff, and the numerous assumptions related to those steps. A main conclusion from the analysis is that uncertainty over the dimension of such a subsidy is large, and is mainly related to uncertainties in how costs of renewable technologies change over time, in the mixes of renewables that individual countries choose to adopt, and in the share of new investment for electricity generation that is channeled into renewables.