Improving total factor renewable energy efficiency (TFREE) is crucial for developed countries to achieve a sustainable energy transformation. International trade is an important source of technological progress and may significantly promote TFREE. However, previous studies have largely overlooked the impact of trade on TFREE. To this end, this study attempts to examine the impact of trade on TFREE of 28 major, developed countries. The main findings are as follows: trade significantly improves TFREE; in terms of the magnitude of the effect, export is greater than import, and trade in goods is greater than trade in services. Trade in most industries promotes TFREE, but trade in the ores and metals industry inhibits TFREE. Trade can only promote TFREE in countries with a high human capital level, high renewable energy infrastructure level, and high institutional quality level. The lag effect of trade on TFREE shows an inverted U shape over time; the nonlinear impact of trade on TFREE shows an N shape as TFREE increases. Biased technological progress and technological improvement effects are the main paths for trade to enhance TFREE. This paper can provide a reference for developed countries to formulate appropriate trade policies to improve TFREE.

As the growth poles of regional development, industrial parks realize green transformation, which boosts green development in host cities while potentially generating impacts on neighboring cities. Drawing on the construction practices of national green industrial parks, this paper utilizes China’s city-level panel data spanning 2007–2023 and employs the multi-period DID model and spatial DID model to empirically examine the impacts, transmission mechanisms, and spatial spillover effects of the industrial park green transformation policy on urban green total-factor energy efficiency (GTFEE). The findings indicate that green industrial park construction boosts urban GTFEE by approximately 11.6%, with industrial agglomeration, green technological innovation, and optimized capital allocation serving as its mediating channels. Heterogeneity analysis reveals that green industrial park construction generates stronger improvements in GTFEE for cities in eastern and western China, as well as those with abundant green industrial parks, advanced green finance, ample general higher education institutions, and underdeveloped digital infrastructure. Compared with national-level industrial parks, provincial ones transformed into green industrial parks exert a stronger positive effect on GTFEE. From a spatial perspective, green industrial park construction hinders the improvement in GTFEE in neighboring cities, and the negative spillover effect is more prominent for those that also build such parks.