The most efficient tilt for photovoltaic panels in El Paso, Texas at a latitude of 31.85°:
Your photovoltaic panels need to be angled facing south.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 27.3°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 8.6° in summer months and 47.1° in winter months.
If you're planning to change the angle of your photovoltaic panels each season, the most efficient angle is 5° in summer months and 52.3° in winter months, and 28.9° in autumn and spring months.