2.6.1. GHG Payback Time

GHG payback time (GPBT) is defined as the number of years it takes solar PV system to pay back its embodied emissions through solar PV generation. The GPBT [41] is described by Equation (11):

$$GPBT = \frac{CO\_2\,\,equivalent\,\, (eq)embed}{CO\_2\,\, eq\,\, avoided\,\, (year)}\tag{11}$$

where,

 $\text{CO}\_2\text{ }eq\text{ }emb\text{ }add = \text{CO}\_2\text{ }eq\text{ }mudules + \text{CO}\_2\text{ }eq\text{ }muniting\text{ }structures + }$  $\text{CO}\_2\text{ }eq\text{ }electric\text{ }(BOS) + \text{CO}\_2\text{ }eq\text{ }transport\text{ }etc$ 

*CO*2 *eq avoided* (*year*) = Emissions avoided per year due to the production of electricity from the solar PV system installation.
