The transition of the German energy system towards renewable energy carriers triggers considerable cost for private households. Costs are passed through to households by a surcharge per kWh. This effectively leads to high cost burdens for poorer households relative to wealthier households. We discuss the issue from the perspective of social justice and argue that costs are distributed in an unfair manner. In the light of rising cost of renewable energy promotion, affordability of energy amongst the poorest should receive increasing attention. Measures of fuel poverty and deprivation with respect to energy could serve as adequate ex-post indicators of non-affordability and should be considered in Germany.