The best roof orientation for the Seattle region is SE to SW with South being the best. SE to SW orientations will result in only a slight annual energy reduction of 2% to 4%. Even due West or East orientations are workable, but you can expect anywhere from 12% to 18% less production than a Southern orientation. If you have no shading issues then adding a couple more solar modules to your system size will compensate for these losses. The best roof pitch or tilt angle is 15° to 45°, with only 2% to 4% loss compared to the perfect pitch. Even a flat pitch will only result in about a 10% annual output reduction; however, we recommend to never have a flat array due to major soiling issues that will require unacceptable maintenance schedules and reduction of the system life.