The key here is they feel that Tesla customers will be interested in solar, and that Solarcity customers are interested in Tesla. Offering new products to the s

The key here is they feel that Tesla customers will be interested in solar, and that Solarcity customers are interested in Tesla. Offering new products to the same customers works great - the core of every business is acquiring customers, and selling more (and related) products to the same customers conserves that core effort. The disaster is when a company takes on a new product for /new customers/. That is when a company's efforts are diluted.