PV Array Azimuth Calculator

A PV array azimuth calculator compares the installed or proposed Array azimuth with a project Reference azimuth and converts the directional difference into an orientation-based energy screening factor. The result is used during early PV layout review to compare roof planes, ground-mount rows, alternate array orientations, and site-model assumptions before production modeling is completed.

The calculator produces three values:

• Azimuth offset — the shortest angular difference between the two azimuth inputs.
• Azimuth alignment factor — a cosine-based multiplier representing alignment with the reference direction.
• Screened daily energy — the entered Baseline daily energy multiplied by the azimuth alignment factor.

This is an orientation comparison calculation. It does not establish PV system output, conductor ampacity, inverter loading, branch-circuit current, feeder size, voltage drop, or utility-interconnection capacity.

Azimuth Inputs

Array azimuth is the compass direction the PV array faces, entered using a 0 to 360 degree convention:

Compass direction	Typical azimuth
North	0 deg or 360 deg
East	90 deg
South	180 deg
West	270 deg

For example, an array facing due south is entered as 180 deg. An array facing southwest might be entered near 225 deg, subject to the actual roof geometry or mounting layout.

Reference azimuth is the orientation used by the site model, conceptual design, or project assumption. It may represent a preferred array direction, a baseline roof plane, or an assumed orientation used to establish the entered energy baseline.

Baseline daily energy is a separately documented energy value in kWh/day. The calculator does not derive this baseline from module wattage, irradiance, inverter efficiency, roof pitch, temperature, shading, or weather data. It applies the orientation factor to the value entered.

Circular Azimuth Offset

Azimuth is circular. North at 0 deg and north at 360 deg are the same direction, so a direct subtraction can produce an incorrect difference near the 0/360 boundary.

The calculator uses the shortest circular difference:

\(\displaystyle \text{Azimuth offset} = \min\left( \left|A-R\right|, 360-\left|A-R\right| \right)\)

Where:

• A = Array azimuth
• R = Reference azimuth

For an Array azimuth of 350 deg and a Reference azimuth of 10 deg:

\(\displaystyle |350-10|=340 \text{ deg}\)

\(\displaystyle 360-340=20 \text{ deg}\)

The Azimuth offset is therefore 20 deg, not 340 deg.

This approach keeps the calculation aligned with physical orientation. Two arrays positioned 20 degrees to either side of the reference direction have the same angular offset under this formula.

Azimuth Alignment Factor

The calculator applies a cosine relationship to the azimuth offset:

\(\displaystyle \text{Azimuth alignment factor} = \cos\left( \frac{\pi}{180} \times \text{Azimuth offset} \right)\)

The result is shown as a multiplier, identified in the interface as Azimuth alignment factor.

At an offset of 0 deg:

\(\displaystyle \cos(0)=1\)

The alignment factor is 1 x, meaning the array and reference azimuth are aligned.

At an offset of 60 deg:

\(\displaystyle \cos(60^\circ)=0.5\)

The alignment factor is 0.5 x. Under this screen’s calculation basis, the entered baseline energy is reduced by one-half.

The factor becomes negative for offsets greater than 90 degrees. That mathematical result reflects the cosine formula; it is not a physical PV production prediction and should not be treated as a negative-energy output estimate.

Screened Daily Energy

The energy result is calculated as:

\(\displaystyle \text{Screened daily energy} = \text{Baseline daily energy} \times \text{Azimuth alignment factor}\)

The result is expressed in kWh/day.

This value can support a preliminary comparison between proposed PV orientations. For example, if two roof planes use the same documented baseline and differ primarily in azimuth, the screened result provides a consistent directional comparison before a full production model is available.

It should not be used directly to set inverter capacity, DC-to-AC ratio, battery capacity, service load assumptions, PV output-circuit conductor size, feeder ampacity, or overcurrent protection. Those decisions require the applicable equipment ratings, electrical design data, installation conditions, and project requirements.

Calculation Example

Assume the following entries:

Field	Entered value
Array azimuth	180 deg
Reference azimuth	180 deg
Baseline daily energy	10 kWh/day

1. Determine azimuth offset

\(\displaystyle \text{Azimuth offset} = \min(|180-180|, 360-|180-180|)\)

\(\displaystyle \text{Azimuth offset}=0 \text{ deg}\)

\(\displaystyle \text{Azimuth alignment factor}=\cos(0^\circ)=1\)

\(\displaystyle \text{Screened daily energy}=10 \text{ kWh/day} \times 1\)

\(\displaystyle \boxed{\text{Screened daily energy}=10 \text{ kWh/day}}\)

The displayed result is:

Result	Value
Azimuth offset	0 deg
Azimuth alignment factor	1 x
Screened daily energy	10 kWh/day

Electrical Design Boundary

The PV Array Azimuth Calculator evaluates directional alignment only. It does not model solar resource, seasonal sun path, module tilt, horizon obstruction, row-to-row shading, rooftop obstructions, soiling, module temperature, tracking, inverter clipping, DC losses, AC losses, weather variation, utility interconnection, or code compliance.

Electrical design remains a separate process. PV source-circuit and output-circuit conductor selection must be based on the actual electrical design current, conductor insulation rating, terminal rating, ambient conditions, rooftop temperature conditions where applicable, current-carrying conductor adjustment factors, routing method, raceway fill, voltage-drop design criteria, and equipment manufacturer instructions. Final installation requirements are subject to the adopted code, project documents, and the authority having jurisdiction (AHJ).