How much energy required to make a Watt of PV? [1].
Fraunhofer study - 1 year payback time, meaning 20x energy EROI over 20 years. [2]

Embodied Energy of PV

Component	Description	Typical Embodied Energy Share (% of module)
Silicon Feedstock & Ingot	Quartz → polysilicon → crystal growth (Czochralski or similar)	25–40%
Wafering	Slicing ingots into wafers (kerf loss, sawing energy)	10–20%
Cell Processing	Doping, diffusion, etching, deposition (PECVD), metallization	15–25%
Glass (Front Sheet)	Tempered low-iron solar glass (~3–4 mm)	10–20%
Encapsulant (EVA/POE)	Polymer layers for lamination	3–8%
Backsheet (or rear glass if bifacial)	Polymer backsheet or second glass layer	3–10%
Aluminum Frame	Extruded frame + finishing	5–15%
Junction Box & Wiring	Diodes, copper wiring, connectors	2–5%
Module Assembly	Lamination, curing, handling, factory overhead	3–8%
Total		~100%

For Upgraded Metallurgical Grade Silicon

About 30% lower overall energy requirement over standard PV.

Component	Description	Typical Embodied Energy Share (% of module, UMG silicon)
Silicon Feedstock & Refining (UMG)	Metallurgical silicon upgraded via slag refining / directional solidification (no Siemens process)	10–20%
Ingot Growth	Crystal growth or casting (lower purity requirements than electronic-grade)	10–20%
Wafering	Slicing or kerfless wafer production	10–20%
Cell Processing	Doping, diffusion, passivation, metallization	20–30%
Glass (Front Sheet)	Tempered low-iron solar glass (~3–4 mm)	15–25%
Encapsulant (EVA/POE)	Polymer layers for lamination	5–10%
Backsheet / Rear Glass	Polymer backsheet or second glass layer (bifacial increases share)	5–15%
Aluminum Frame	Extruded frame + finishing	8–18%
Junction Box & Wiring	Diodes, copper wiring, connectors	2–5%
Module Assembly	Lamination, curing, factory overhead	5–10%
Total		~100%