Grid connected PV systems, or GCPVS, produce clean and renewable energy through the
photovoltaic e ect in the operation stage of the power plant. However, this is the penultimate stage of
the facilities before its dismantlement. Before starting generating electricity with zero CO2 emissions,
a negative energy balance exists mainly because of the embodied energy costs of the PV components
manufacturing, transport and late dismantlement.
First, a review of existing studies about energy life cycle assessment (LCA) and Carbon Footprint
of PV systems has been carried out in this paper. Then, a new method to evaluate the Real Energy
Payback Time (REPBT), which includes power looses due to PV panels degradation is proposed and
di erences with traditional Energy Payback Time are analysed. Finally, a typical PV grid connected
plant (100 kW nominal power) located in Northern Spain is studied in these sustainability terms. This
facility has been firstly completely modelled, including PV modules, inverters, structures and wiring.
It has been also considerated the energy involved in the replacement of those components with shorter
lifespan. The PV panels degradation has been analysed through the comparison of normalised flash
test reports on a significant sample of the installed modules before and 5 years after installation.
Results show that real PV degradation a ect significantly to the Energy Payback Time of the installation
increasing slightly a 4:2% more the EPBT value for the case study. However, along a lifespan
of 30 years, the GCPVS under analysis will return only 5:6 times the inverted energy on components
manufacturing, transport and installation, rather than the expected 9:1 times with the classical estimation.
