Since their inception in the early 2000s, sustainable funds where met with initial diversification issues, but has since then evolved to not only be sustainable in a traditional sense, but also financially.This perpetuates the ongoing debate surrounding fund fees, questioning whether funds with high fees generate enough excess returns to justify their management style. To investigate this, equity funds originating from Europe with four or more "Morningstar Globes" were analyzed. Using these criteria, 57 funds were identified, with fees ranging from 0.2% to 2.78%.The study conducts correlation analyses and linear regressions to ascertain any potential relationships. This is achieved by comparing the funds' fees to their historical returns and various measures of risk-adjusted returns: Jensen's Alpha, Treynor's Index, and the Sharpe Ratio.The results indicate that sustainable funds with lower fees tend to yield higher returns. A negative correlation between fund fees and returns was confirmed, suggesting it is advantageous to select funds with as low fees as possible for both short- and long-term investing. The regression was not perfect, indicating the possibility of other factors influencing returns besides fees, consistent with the complexity of financial markets.