Several factors may influence whether it is smart to forego installing the PV array at its “optimal” orientation and tilt for a given location.
Local utility policies may reward grid-tied system orientations that would otherwise not be ideal. For example, time-of-use (TOU) metering may place a premium on energy consumed or produced during the afternoon hours. In this case, a PV array that favors a westerly orientation and produces more energy (and earns credit at the higher rate during peak-load times) may be beneficial.
Local climate characteristics, such as morning fog or regular afternoon thunderstorms, may also influence the ideal array tilt and orientation. Regular morning fog in coastal areas may warrant arrays that favor a more westerly orientation. Many locations in the Rocky Mountains experience afternoon thunderstorms during the summer months and often have winter storms followed by very sunny mornings. The combination of these two weather influences may favor arrays with a slight easterly orientation. In snow country, steeper tilts may be required to help prevent snow buildup and potential ice damming around the modules.
Off-grid PV systems also have special considerations that dictate their ideal orientation and/or tilt. Consider a fixed-mounted off-grid PV array that serves a home with higher energy consumption during the winter months. This home will benefit from an array that’s more steeply tilted to more effectively capture the low winter sun angle. A PV water-pumping system that is used for summertime irrigation and/or livestock watering will require a shallower tilt to take advantage of the high-angled summer sun.