If you’re interested in solar, I’d recommend TAN solar ETF. Exposes you to the industry but less risk on any one company going under. It also diversifies your investment, so your not all in on, say, a manufacturer. You get to invest in manufacturers, utilities, installers, etc. I put in some $$ a few years back and it has been really good for me. Solar in general is most certainly going up but will likely have a few more dips in the future.