<p>The relationship between digital economy and energy conservation and emission reduction (ECER) has attracted much attention, highlighting its importance for green development. Generally, the influence between them is not static, but is affected by several factors. Utilizing panel data spanning from 2011 to 2019, encompassing 250 cities in China, we first established an index system for ECER and measured its development level. To further analyze their complex interplay, a threshold regression model is implemented to examine the nonlinear effects of digital economy on ECER while considering the moderating role of human capital. The empirical findings are as follows: (1) The impact of digital economy on ECER exhibits an acceleration positive threshold effect influenced by the adjustment of human capital. (2) The nonlinear effect of digital economy on ECER varied depending on industrial structure and region. Based on these findings, policymakers can acquire a more nuanced comprehension of the specific performance of various cities in China in the field of ECER, and unleash digital economy potential in ECER based on the characteristics of each city’s industrial structure and regional advantages, so as to promote green and sustainable development.</p> Graphical abstract <p></p>