Gray energy is the amount of energy required to produce, transport to the place of use, and dispose of a product or material or to secure a service. Gray energy can also be called "virtual energy," "frozen energy," or "hidden energy".

Generally, the term gray energy refers to a methodology for assessing the total amount of energy used throughout the product's life: raw material extraction, transportation, processing, assembly, installation, as well as demolition and disposal. Some methodologies aim to express gray energy in terms of the amount of oil consumption required; other methodologies evaluate gray energy in terms of the amount of sunlight that is used in ecological processes.
EMBOYED ENERGY (GY) Natural Stone Alluminium Copper Timber Fabric Glass Plaster Ceramics Masonry Plastic Steel Concrete 10 25 30 40 40 48 60 80 95 140 140 210 0 50 100 150 200 Commonweath Scientific and Industrial Organisation (CSIRO)