The grid is designed to handle variability in energy supply, as new and different generation sources are implemented onto the grid. An increasing amount of solar energy is being reliably integrated onto the grid with the help of detailed weather reports. This allows grid operators to adjust other electricity sources as needed. When solar power diminishes, grid operators can draw on reserves from other sources. Also, while storing large amounts of electricity is difficult, storing thermal energy that can later be converted into electricity is relatively easy.