Pros
Sunrun's goals are unusually bold, even for a Silicon Valley tech startup: Sunrun is re-inventing a fundamental consumer experience (residential electric service) and thereby bringing competition to an industry that previously has had none. With goals this big (creating not only a product, but a new product category and a new market), there is a ton of meaningful work to do at the company. Every department, from accounting to engineering, is pushing on the boundaries of their respective fields. In fact, there is more work at Sunrun than there are people to do it. For an employee, this means 1) opportunity for learning and career advancement, 2) a culture that values judgement, particularly when setting priorities, 3) a meritocracy that rewards employees who get stuff done and 4) a work environment where your fellow employees are genuinely excited because they are working on meaningful problems.
Cons
Sunrun is a small company with huge goals and challenges. Unsurprisingly, this means that many things at the company are in flux. If you are the type that wants to grab an undefined project or process and solve it, you will do well. If you are the type that needs pre-existing structure and processes to succeed, you could struggle in the fast-paced startup environment at the company.