Siting Your Small Solar Electric System
Both the orientation and tilt of your solar panels or photovoltaic (PV) modules will affect your solar electric system. You and your contractor should consider both factors while evaluating your site's solar resource and sizing your system.
PV modules should be oriented geographically to maximize the amount of daily and seasonal solar energy that they receive. In general, the optimum orientation for a PV module in the northern hemisphere is true south. However, your modules can face up to 45º east or west of true south without significantly decreasing its performance.
If you plan to mount the modules on your roof, you'll also want to consider these factors:
To be eligible for some rebates, your system must be unshaded between certain hours during certain times of the year. Some states also have laws that establish your right to protect your solar access through the creation of a solar easement.
If a rooftop can't be used, your solar modules can also be placed on the ground, either on a fixed mount or a "tracking" mount that follows the sun to orient the PV modules.
Most PV modules are mounted flat on the roof, and so have the same tilt as the roof. Although the optimal tilt angle for your modules is an angle equal to your latitude, fixing the PV modules flat on an angled roof is generally not a problem. However, because most roofs are pitched at an angle less than the latitude, you and your contractor will need to factor your roof angle into the performance calculations when sizing your system.