Pros
I'm really happy I worked at SUN. There's a lot of passion here. Everyone cares about how to combat the legal and systemic barriers to maximizing solar's economic and environmental impact. The people are amazing. Everyone is kind and empathetic. You'll make real friends here. For a lot of employees, SUN is a remote-friendly environment. There's an office in DC, and staff travel for retreats, but plenty of people work entirely from home. The exception to this is the staff members whose work involves community organizing and engagement. Focus Thursdays are a highlight. No one has any meetings from 1 p.m. EST onward each Thursday, so people can get work done or take care of odds and ends. The benefits are top-notch. In addition to insurance, employees get a 401k and professional development stipends. There's also a generous vacation and sick leave package.
Cons
A lot of my feedback is applicable to most nonprofits — pay, career growth, etc. By the time I left, management was actively looking to address a lot of my concerns.