Of course, if you like solar energy stocks, you can go all in on this narrow segment of the green energy marketplace with a dedicated clean energy ETF that's also provided by asset manager Invesco and commands more than $3 billion in assets under management. With more than 50 holdings in its portfolio including Enphase, SolarEdge Technologies Inc. ( SEDG ), Sunrun Inc. ( RUN ) and First Solar Inc. ( FSLR ), it's a who's who of the solar sector. If you're not afraid of putting all your eggs in one basket within clean energy, TAN is a popular and accessible option.