This paper analyses the effect of recognizing co-firing coal with biomass as renewable electricity. We provide simulations for the French and German electricity mix. Results indicate that, if co-firing is recognized as a renewable, coal may crowd-out traditional renewables with increased generation and additional investments. Regarding CO2 emissions, we find surges when co-firing is recognized as a renewable. The rise is more significant in Germany due to greater coal capacity. In France, the magnitude depends on the share of nuclear with a lower increase when old nuclear plants are prolonged. Finally, we find that recognizing co-firing as a renewable reduces the overall costs for electricity. We balance the cost saving with the increased social cost from higher CO2 emissions. Results show that the cost saving is lower than the increased carbon cost for society with carbon valuation around 100 Euros/tCO(2), except in France when old nuclear plants are not decommissioned.