PV Array Tilt Calculator

A PV Array Tilt Calculator compares a fixed Array tilt against the site’s latitude reference and produces a Tilt alignment factor and Screened daily energy. The result is useful during early PV layout review when a documented daily-energy baseline must be normalized for a different fixed tilt assumption.

The calculator does not establish PV system production. It applies a geometric cosine relationship between the entered tilt and the absolute Site latitude, then applies that factor to Baseline daily energy.

For a fixed array, the result can support preliminary comparisons between proposed rack angles, roof slopes, or ground-mount tilt assumptions. It may also help identify whether an orientation change is large enough to require a revised production model, conductor loading review, equipment selection review, or financial forecast.

Inputs and Results

Field	Electrical and layout use
Site latitude	The installation latitude in degrees. The calculator uses the absolute value, so a signed latitude is treated as the same distance from the equator as its unsigned value.
Array tilt	The fixed PV module plane angle measured from horizontal, in degrees. A flat array is 0 degrees; a vertical plane is 90 degrees.
Baseline daily energy	A separately documented daily-energy value in kWh/day used as the starting point for the orientation comparison. It is not calculated by this screen.
Latitude reference tilt	The absolute value of Site latitude, in degrees. It is the reference angle used for comparison.
Tilt offset	The absolute angular difference between Array tilt and Latitude reference tilt.
Tilt alignment factor	The cosine-based multiplier produced from the tilt offset. A value near 1.0000x indicates close alignment with the latitude reference.
Screened daily energy	Baseline daily energy multiplied by the Tilt alignment factor. This is a comparative energy screen, not a modeled generation forecast.

Tilt Alignment Formula

The calculator first establishes the latitude reference:

\(\displaystyle \text{Latitude reference tilt} = |\text{Site latitude}|\)

It then calculates the difference between the fixed array position and that reference:

\(\displaystyle \text{Tilt offset} = \left| \text{Array tilt} - \text{Latitude reference tilt} \right|\)

The tilt offset is converted into a cosine multiplier:

\(\displaystyle \text{Tilt alignment factor} = \cos(\text{Tilt offset})\)

The cosine function uses the tilt offset expressed in degrees for field input, with the angle converted as required for calculation.

Finally, the baseline is adjusted:

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

A 0-degree tilt offset produces a 1.0000x alignment factor. As the offset increases, the cosine factor falls below 1.0000x and reduces the screened daily-energy value.

Calculation Example

Use the following entered values:

Input	Value
Site latitude	35 deg
Array tilt	30 deg
Baseline daily energy	10 kWh/day

Step 1: Determine Latitude Reference Tilt

\(\displaystyle |35| = 35 \text{ deg}\)

Latitude reference tilt = 35 deg

Step 2: Determine Tilt Offset

\(\displaystyle |30 - 35| = 5 \text{ deg}\)

Tilt offset = 5 deg

Step 3: Apply the Alignment Factor

\(\displaystyle \cos(5^\circ) = 0.9962\)

Tilt alignment factor = 0.9962 x

Step 4: Calculate Screened Daily Energy

\(\displaystyle 10 \text{ kWh/day} \times 0.9962 = 9.9619 \text{ kWh/day}\)

Screened daily energy = 9.9619 kWh/day

Under this narrow orientation comparison, a 30-degree fixed array at a 35-degree site latitude retains approximately 99.62% of the entered daily-energy baseline.

Electrical Design Use

PV tilt is primarily an array-layout and energy-assumption input, but the energy model it informs can affect downstream electrical design decisions. A revised production estimate may change expectations for annual output, battery dispatch, inverter loading patterns, load offset, and project economics.

It does not directly calculate DC conductor ampacity, PV source-circuit current, inverter output current, branch-circuit loading, feeder ampacity, voltage drop, raceway fill, or required AWG or kcmil conductor size. Those determinations require the actual electrical design inputs, including module and inverter electrical ratings, circuit configuration, conductor insulation temperature rating, terminal rating, ambient conditions, rooftop temperature conditions where applicable, current-carrying conductors, correction factor, adjustment factor, and the installation requirements accepted by the AHJ.

For preliminary layout work, the screened result can indicate whether a proposed roof pitch or rack angle is reasonably close to the selected latitude reference before committing the assumption to a full PV production and electrical design workflow.

Orientation Boundary

The calculation compares Array tilt with absolute Site latitude and applies a cosine alignment factor to Baseline daily energy. It does not model solar-resource data, seasonal sun path, azimuth, weather, cloud cover, shading, soiling, module temperature, bifacial response, tracking, inverter clipping, losses, structural loading, utility interconnection, equipment listings, or code compliance.

Use a site-specific production model and the project’s engineering, manufacturer, permitting, and AHJ requirements before relying on energy assumptions for final system design, electrical sizing, structural design, or utility documentation.