Is your goal financial return, or promoting an environmental / energy efficient future? Both? I think people usually mean the former when they say "invest" but it might mean either.
If it fits your goals, looking for a community solar or municipal energy plan with a green/local option can provide additionality, and 'less climate catastrophe' / 'more energy independence' are kinds of return on investment I value.
Though I'd also like my retirement funds to be supporting / depending on value from non fossil fuel.