What is the optimum tilt for a fixed array?

For maximising annual energy, a fixed array tilted roughly equal to the site latitude facing the equator is near optimal. Lower tilts favour summer, higher tilts favour winter, and this tool compares your chosen tilt against the latitude-equal benchmark.

How much does facing away from south cost?

Modest azimuth errors are forgiving. Facing 30 degrees east or west of south typically loses only a few percent of annual yield, while east or west walls lose 15 to 20 percent. The model captures this falloff with a cosine-shaped azimuth penalty.

Is this model accurate enough to design a system?

It is a quick screening estimate, not a substitute for hourly simulation tools like PVWatts or PVsyst that use real meteorological data. Use it to compare orientations and rule out poor ones, then confirm the chosen layout with a full simulation.

What does 0 percent azimuth mean?

Azimuth here is the deviation from true south, so 0 means the array faces due south, which is optimal in the northern hemisphere. Enter negative values for east-facing and positive for west-facing. Southern-hemisphere sites should mirror this around due north.

Why does a flat array still produce a lot?

A horizontal array, 0 degrees tilt, captures diffuse light from the whole sky and still yields 85 to 90 percent of the optimum in many climates. It is azimuth-independent but collects dust and rain poorly, which the geometric model does not penalise.

Solar Array Tilt & Azimuth Output Calculator

Most roofs are not perfectly tilted and aimed due south, and this calculator estimates the energy cost of that compromise. It compares your array’s tilt and azimuth against the latitude-tilt, south-facing optimum using a simplified geometric transposition model.

How it works

Two penalties combine. The tilt penalty falls off as your tilt departs from the latitude-equal optimum, and the azimuth penalty follows a cosine-shaped curve as you turn away from due south:

tiltFactor = cos(tilt − latitude)         clamped to a diffuse floor
azimuthFactor = 1 − k × (1 − cos(azimuth))
yield % = tiltFactor × azimuthFactor × 100   (relative to optimum)

The diffuse floor keeps even a poorly tilted array from dropping to zero, since panels always collect scattered sky light.

Notes

This is a screening estimate to compare orientations quickly. For a final design use an hourly tool such as PVWatts or PVsyst with local weather data.

Tips

Tilt near your latitude maximises annual energy on a fixed mount.
Azimuth within 30 degrees of south costs only a few percent.
East or west orientations can still be worthwhile where roof space is free.