The objectives of this paper are to estimate and discuss the penetration levels that are technically feasible by solar and wind grid-intertie electric systems that do not include any storage. The associated capacity credit of such systems are also assessed. The results of this study are based on hour-by-hour year-long simulations of how different sizes of such renewable energy systems behave in three widely different geographic locations in the US under three different synthetic electric load scenarios. We find that no energy dumping occurs for penetration levels (defined in terms of peak loads and not average output) up to 0.5 for all-wind systems and up to 0.6 for all-solar systems. These figures correspond to 10-25% of the annual electric energy. Capacity credit of solar systems are around 28-38% for low penetration levels decreasing to 15-20% for penetration levels of 0.5. Those for wind systems are lower and more variable : 1030% for penetration levels of 0.1 and 5-10% for levels of 0.5.