**4. Discussion**

It can be observed that the results are generally in line with the results obtained in previous studies of a similar type (see Tables 1 and 4). This study extends the research to cover the unlisted German companies that have, to the best of our knowledge so far been left "unattended" by previous research. The results presented here widen the scope of knowledge we have about the factors that affect the profitability of companies operating within the German RE industry. In this respect, the finding is that the unlisted companies do not differ from the previously studied companies listed.

Based on the results, it is clear that the firm-specific determinants outrank the industryspecific counterparts in importance, as was also suggested by the previous studies. One of the findings is that company size in terms of assets matters when the firm is large and that the size in assets has a negative effect on the profitability of large firms. The size of assets is not significant with regard to the profitability of the SMEs. This result is supported by previous research [23] that suggested that the rapid expansion of firms may have a negative influence on profitability, implying that large firms may follow costly strategies to gain a bigger share of the markets. One explanation could be that in an investment phase (which is ongoing on the German RE markets), there are profitability lags. The capital investment intensity (data which was not available for this analysis) is also proven to be a determinant of profitability and could explain the negative effect of the assets in case the effect of the capital investment intensity is significantly negative for larger firms, as was pointed out by the previous research.

The positive relationship between the liquidity and profitability of the SMEs may be an implication of the power of slack income that the firms can invest to generate profit. Then again, leveraging profit might be the chosen strategy for large firms that have the position to take more risks. Nonetheless, too many and/or far-fetching conclusions should not be drawn about the determinants that appeared significant less consistently in the analysis.

The average Feed-in-Tariff had a negative effect in most of the tests with the SMEs and in three tests with large firms. These findings are not in line with the previous results [27,31] and our expectations. The previous analyses found that the FIT has a positive effect on the profitability of electricity firms, but the data used were from the companies that in fact received support from the FIT. The share of FIT-supported firms in the data used in this study is unknown to us. Thus, the negative effect result may be caused by the effect of FIT on firms that did not receive FIT-support and were affected negatively by the support their competitors received. The authors conclude that the counter-intuitive result can also be a consequence of the aggregation method used in treating the variable and the reader is suggested to take the result as preliminary.

The change in electricity consumption had a negative effect on profitability, as suggested by previous studies (in past studies energy consumption was analyzed, instead of electricity consumption). This result may reflect the increasing competition in the industry, as the demand has only increased during the period of the analysis in terms of the final electricity consumption in the country. Furthermore, the trend of the market concentration growth rate in the data of this analysis shows that the competition is intensifying in the industry structure, and this seems to especially benefit especially the SMEs according to the analysis. Moreover, the share of renewables seemed to be beneficial for both the SMEs and large companies.
