How to choose a tilt angle
Panels produce the most when sunlight hits them straight on. A fixed mount can only be right on average, so the best year-round angle is a little less than your latitude. Adjustable mounts gain extra energy by tilting steeper in winter and flatter in summer.
Formulas from Charles R. Landau's optimum tilt analysis.
Example: Denver (39.7° N)
Year-round: 39.7 × 0.76 + 3.1 = 33.3°. Winter 64.7°, summer 12.2°.
Orientation
In the Northern Hemisphere, face panels true south. East- or west-facing arrays lose about 10–20% of annual output. On most roofs, the difference between the ideal angle and the roof pitch is small, so flush mounting is usually the best value.
Frequently asked questions
What is the best angle for solar panels?
Roughly your latitude minus a few degrees for year-round output. Across most of the U.S. that is 25–38°.
Is it worth adjusting panel tilt seasonally?
Adjusting twice a year adds about 4–5% energy; four times a year adds a little more. For roof systems it is rarely practical.
What if my roof is flatter than the ideal angle?
A few degrees off costs very little, often under 5%.