The paper investigates the macroeconomics of an energy transition – a shift from brown to green energy production through carbon taxation. Using a medium-scale DSGE model with energy production sectors and endogenous innovation in the green energy sector, we show that an energy transition – initiated through a brown energy tax – resembles a large supply side shock, causing a surge in inflation and energy prices and a decline in consumption. Innovation increases the efficiency of green energy production and drives energy prices down in the medium run. We document that monetary policy plays a critical role for the dynamics and pace of the transition, even if the transition is not explicitly part of the policy rule. A monetary policy with less emphasis on inflation stabilization allows f or temporarily higher inflation and energy prices, which boosts R&D and innovation, enhancing welfare and accelerating the transition.