clouds. Clouds diminish the power of solar panels, especially in habitually foggy or overcast regions. According to the National Renewable Energy Laboratory, The solar resource during foggy or low-cloud conditions is approximately 10% of the value under clear-sky conditions. Solar arrays in Denver, Colorado, would rarely be obscured by clouds, as that city experiences only 30 to 40 overcast days per year. Hilo, Hawaii, despite its proximity to the equator, receives rain an average of 277 days per year, which might make it a poor choice for solar-power generation.