*4.2. Results of Calculations Avoided CO2eq Emission*

Results of LCA model calculations according to the IPCC GWP 100a method showed that the main elements influencing environmental burden in the climate change category are connected with the production of PV systems. Calculation of basic scenarios for monocrystalline and polycrystalline PV systems of 5.72 kWp resulted in estimated emissions of 9421.43 kg CO2eq and 8744.99 kg CO2eq, respectively. Over 82% of these values related to PV panels, while 12% corresponded to BOS and 5% to the servicing. Other unit processes such as transport and installing were characterised by relatively small shares within 1%, which is also reported in related previous studies [67]. These basic values were then differentiated between provinces on the basis of changing transportation distances, kinds of technology used in 2019 and 2020, as well as systems' productivity. The results of individually calculated emissions per functional unit (1 kWh of energy generated by system) and over a 30-year perspective used in the study are presented in Table 3 and Figure 8.

**Table 3.** Results of GWP indicator calculation: S-GWP—GWP indicator calculated for a PV system of 5.72 kWp, kg CO2eq; P-GWP—GWP indicator calculated for installations built during 2019 and 2020 in provinces, Mg CO2eq; FU-GWP—GWP per functional unit, Mg CO2eq/kWh.


**Figure 8.** Monte Carlo results of FU-GWP calculated for the provinces with a confidence interval of 90%.

As can be inferred, FU-GWP differs between provinces, first on the basis of various productivity of PV installation and then transport distances. The correlation between yearly electricity productivity can be observed on the base of Table 1 since the provinces such as Lower Silesia, Opolskie, Silesian, characterised by the highest productivity represent the lowest FU-GWP indicators. The outcomes of calculations are comparable to previous studies on PV systems working in temperate climate conditions [67–69], and smaller FU-GWP indicators result from the higher efficiencies of the analysed PV panels. At the same time, the calculated emission rate is similar to the literature results of the carbon emission rate for PV installations working under similar solar irradiation (1222 kWh/m2/year, Germany), equal to 55 g CO2eq/kWh [70].

Calculation of avoided emission ΔGHG, Mg CO2eq, was based on unit GWP indicators obtained for hard coal (0.966 kg CO2eq/kWh), lignite (1.164 kg CO2eq/kWh), natural gas (0.738 kg CO2eq/kWh), and Polish energy mix called MIX PL (0.804 kg CO2eq/kWh) compared with the data in Table 4 [21,64,71].

According to the data in Table 4 and Figure 9, provinces with the highest number of installations (Lesser Poland, Masovian, Greater Poland, Silesian) contribute to the highest possible reduction in CO2eq emission. The level of CO2eq avoided emission depends on the energy source replaced. The final effects of the "My Electricity" program in accordance with climate change are, therefore, hard to precisely estimate since CO2eq avoided emission is correlated with the predictions on shares of energy sources in the Polish market.

Comparison of the obtained results with previous studies on the existing support programs and their environmental impacts over the world show the potential of carbon emission avoidance determined by local conditions and the scope of calculations. One of the main factors can be defined as the characteristics of grid electricity (energy mix) determining both emission avoidance potential and energy payback time. Thus, in fossilfuel-based countries, the support programs of photovoltaic technology have the potential to contribute to GHG reduction, while in countries with a high share of RES, such as the study by [58,72] using the example of Brazil, the policy should be more carefully defined, in spite of the fact that calculated GHG emissions from photovoltaics can be reduced by the use of PV panel manufactured in low-carbon economics. Still, in some case studies assessing PV distributed generation projects (1255.2 kWp) in the same country, the estimated environmental advantage is nearing 0.48 kg CO2eq/kWh and 19,900 Mg CO2eq over the project lifetime of 25 years [73].


**Table 4.** ΔGHG, Mg CO2eq, calculated for provinces in Poland in 30 years perspective on the basis of individual GWP differences for the energy sources considered to be replaced, kg CO2eq/kWh.

**Figure 9.** ΔGHG, 103 Mg CO2eq in four scenarios of replaced energy source.

According to data presented in [73] on the basics of household cases, many legislative and financial supports need to be implemented to ensure financial accessibility of novel technologies to domestic consumers and to encourage them to participate in balancing local energy demand and supply. A similar trend can be observed in this study, where the fast development of the PV market was stimulated by financial aspects. As presented in [73], average implicit abatement subsidy varies between countries and was estimated as 137–170 USD/1 Mg CO2eq (116–145 EUR/1 Mg CO2eq) for Germany, with avoidance potential 0.521 kg CO2eq/kWh [74]. It should be noted that higher avoidance potential in this study results from the energy mix and close to 0.748 kg CO2eq/kWh. Assuming that the energy produced from burning hard coal is replaced by energy from photovoltaics, the savings will amount to 35 million tons of CO2. With the current prices of CO2 emission allowances of around EUR 50 (Figure 1), the "My Electricity" program will save EUR 1550 million with an expenditure of EUR 251 million. Taking into account the total installation costs of 1010 EUR/kWp [75,76], they are still lower than the costs of CO2 emission rights over 30 years.
