Due to significant cost advantages, wind energy penetrated the energy mix of most large countries much faster than solar PV did until the recent decade. However, Japan has been almost one-sidedly leaning toward the more expensive solar PV. For using solar PV electricity, the Japanese consumers are also paying sizably higher tariffs than those in other countries, especially after the Fukushima nuclear accident in 2011 that led to the sudden suspension of all nuclear power plants. Japan's energy transition towards renewables is accordingly largely single legged, rather than more balanced to take advantage of both wind turbines and solar PV. This article explains the puzzle on why renewable energy development in Japan has created such a wide distance from more economically optimal situations. We focus on the initiation, formation and impacts of the solar lobby that comprises bureaucracies, politicians, solar PV manufacturers, and independent power producers. Policy implications are drawn for Japan and other countries on the importance of controlling political lobby to achieve less costly energy transition. •Japan's energy transition focuses much more on expensive solar PV but not on wind.•We examine Japan's solar lobby to explain the deviation away from economic optimum.•Solar lobby evolved dynamically to pivot on different interest groups over time.•The development of solar lobby (vs. Wind lobby) showed path dependency.•Political lobby should be effectively addressed for better energy transition.