节能 (jié néng) literally means 'to save energy' — 节 (jié) means 'to conserve, economize, or moderate', and 能 (néng) means 'energy' (short for 能源, néngyuán). Together, they form an adjective describing devices, behaviors, policies, or technologies designed to reduce energy consumption without sacrificing functionality. It’s commonly used in environmental, industrial, and household contexts — for example, when describing appliances with high efficiency ratings or government initiatives promoting sustainable development.

The term often appears in compound nouns like 节能灯 (jié néng dēng, 'energy-saving lamp') or 节能减排 (jié néng jiǎn pái, 'energy saving and emission reduction'). While it functions primarily as an adjective, it can also serve as a noun in phrases like '提倡节能' ('promote energy saving'). It carries a positive, socially responsible connotation and is widely used in official discourse, product labeling, and daily conversation about sustainability.