Several countries and states have set targets for substantially increasing renewable energy (RE) contributions in their electricity grids. As the potential for additional hydro-electricity is limited in the US most future RE penetration is envisioned to be in the form of wind and solar. Our simulations, based on hourly resource and load data, demonstrate the maximum penetration achievable in the grid managed by the New York Independent System Operator (NYISO), by wind- and solar-power independently, and when they are combined.