美國社群太陽能立法對太陽能採用之影響

Abstract

社群太陽能是一種共享光電模式，參與者可以購買或租賃部分比例的大型太陽光電系統，而不必在自家屋頂或土地裝設，並可獲得與持有比例相應的電費收益或抵減。如此一來，過去無法或不願安裝光電板者，也能藉此參與再生能源發展並共享其成果。為推動社群太陽能，自2008年起，美國陸續有多個州通過了相關法規。然而，這些州級政策的實際效果尚未獲得充分研究。本研究填補了此一研究缺口，探討州級社群太陽能立法對太陽光電裝置容量的影響。研究採用合成雙重差分法，透過對未實施政策的州和政策實施前的時期進行加權，以建構控制組。此方法確保了政策實施前，實驗組和對照組的裝置容量趨勢保持平行，以利比較政策前後、實驗組與對照組之間的差異。本研究兼論社群太陽能是否對屋頂太陽能的採用產生外溢效果。結果顯示，在2017年之前頒布政策的州，社群太陽能的裝置容量顯著增加，且未對屋頂太陽能的採用造成替代效應。這份研究貢獻了社群太陽能政策有效性的實證證據，並闡釋了不同太陽能市場間獨立或互相影響的關係。

Bearing the mission of accelerating renewable energy development and engaging a broader population, community solar allows its participants to own or lease a portion of large solar energy systems and get rebates on utility bills. To encourage the adoption of community solar, several U.S. states have passed legislation since 2008 and in the following years. However, the effectiveness of these state-level community solar policies remains unexplored. This study addresses this gap by examining the impact of state-level community solar PV legislation on solar installation capacity in the U.S. To estimate the effects of the inception of community solar legislation on solar PV adoption at the state level, I leverage the synthetic difference-in-differences approach, by which I construct a control group by weighting a combination of untreated states and pre-treatment time periods, ensuring that pre-intervention trends in solar capacity are parallel between treated and untreated states. I also investigate if community solar has any spillover effect on the adoption of rooftop solar. The results show that the state policies significantly increased community solar capacity in states with policies enacted before 2017 and did not substitute rooftop solar adoption. The paper not only provides some of the first evidence on the effectiveness of community solar in promoting solar adoption but also sheds light on the dynamics between different solar markets.