Each of Elon Musk’s businesses are interconnected in the short and the long term.
Both Tesla’s and SolarCity’s mission is to accelerate world’s transition to sustainable energy by offering affordable energy products.
1. SolarCity supplies solar panels to Tesla’s charging stations, helping the company provide recharging to drivers at zero cost.
2. Along with battery packs, Tesla’s Gigafactory makes Powerwall and Powerpack that SolarCity sells to its end customers as a backup during grid outages.
SolarCity reduces Tesla’s operational cost with solar panels and Tesla makes solar panel installation viable by supplying energy storage products.
This vertical integration of energy products reduces Tesla’s battery cost through economies of scale. Thus, achieving affordability.
Reference: ‘Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future’ by Ashlee Vance