Because PV panels are able to capture more solar energy when they are pointed directly at the sun, installers may configure systems to optimize output by adjusting the orientation and tilt of a system, or by using mechanisms that track the sun as it traverses the sky.
We generally determine the tilt of a ground mount system (the angle between the module and the horizontal) to optimize overall or seasonal performance. Assuming that a system has tilted modules, we generally set the orientation (direction) of that tilt to optimize overall or time-of-day performance. In the Northern Hemisphere, the simplest way to maximize total annual system output of a fixed-tilt system is to tilt the panels south. The tilt angle may increase with latitude: the farther away from the equator, the higher the tilt.
However, while solar radiation peaks around noon, electricity demand often peaks in the afternoon or early evening. In these last few hours of daylight, west-facing PV panels have an advantage over south-facing panels, as they're tilted towards the setting sun. Higher PV output at this time of day is often beneficial to grid operators working to increase electric supply to balance high levels of demand, but customers generally will not see this benefit unless they are on time-of-use electric rates. For example, under net-metering arrangements, the financial benefit of these PV systems is based on the quantity of kWh generated, regardless of the time of day.