Gray energy is the amount of energy required to produce, transport to the place of consumption, and dispose of a product or material or to provide a service. Gray energy may also be referred to as "virtual energy", "frozen energy", or "hidden energy".

In general, the use of the term gray energy is accompanied by an indication of the methodology applied for evaluating the total amount of energy used during the entire lifetime of a product: extraction of raw materials, transportation, transformation, assembly, installation, destruction, and disposal. Some methodologies are based on the expression of gray energy in terms of the required oil consumption, while other calculate gray energy based on the amount of sunlight 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)