The amount of solar energy that hits Earth every day is large enough to power the world many times over with carbon-free electricity. Continuous technology innovation and increasing scale of the solar power technologies we have today has resulted in dramatic cost reductions and a clear path for solar power to achieve electricity costs of 5c/kWh or less that are directly cost competitive with traditional forms of electricity generation in many parts of the world. However, cost reductions significantly below these levels will be required to 1.) allow large penetrations of solar power onto the grid to be competitive from a system-wide perspective – to account for the added costs of energy storage and other grid upgrades that may be required to accommodate growing amounts of solar – and 2.) allow solar power to cost effectively decarbonize other sectors through the production of low carbon transportation fuels and industrial materials. A new generation of transformational solar power technologies, beyond what we have today, will need to be developed to achieve these dramatic continued reductions in the cost of solar power.