<p>Against the backdrop of an increasingly severe climate crisis and frequent extreme heat events, accelerating the energy transition has become an urgent imperative for all countries. However, systematic research is lacking on how renewable energy technology spillover based on patent citations drives the energy transition in host countries and what moderating role extreme heat events play. To fill this research gap, this article, firstly, explores the impact of renewable energy technology spillover from China based on patent citations (RETSFC) to the energy transition in 20 countries from 2000 to 2022 by using panel regression model. Then, heterogeneity analysis is carried out from the technology types and the renewable energy endowments in host countries. Lastly, the moderating mechanism of extreme heat events is revealed by developing a nonlinear moderating effect model. The results show that: (1) RETSFC plays a significant driving role in energy transition, in which wind power technology spillover has the greatest promotional effect. (2) RETSFC shows a strong coupling effect with the renewable energy endowments in host countries, having greater influence on the countries with better endowments. (3) RETSFC exhibits climate change adaptation. The main manifestation is that low-frequency extreme heat events diminish the impact of RETSFC, whereas high-frequency events enhance it. Moreover, historical extreme heat events show a significant positive moderating role. This study not only enriches empirical research on technology spillover in energy transition, but also provides new insights into identifying the role of extreme heat events.</p>