I treat it like a riskier CD, no more no less.
No one was worried about vast amounts of people no longer paying their subprime mortgages either. Not saying your investment strategy is wrong, but "predictions are difficult, especially about the future".
The prospectus https://solarbonds.solarcity.com/assets/bond_document/180/?f... lists the following risks (among others).
• your inability to initiate bankruptcy proceedings against SolarCity;
• the lack of certain “customary” investor protective covenants in the indenture;
• your inability to require us to repurchase the Solar Bonds upon a change of control of SolarCity;
• lack of cross-default provisions in the indenture with respect to our other debt; and
• the lack of an underwriter to conduct third party due diligence and other types of “gatekeeper” actions typically taken by an underwriter in an underwritten public offering.