How do I use the Azimuth Deviation Loss Calculator?

Enter the requested values using the units shown, choose the options that match your case, calculate the result and review the displayed formula or working before using the answer.

Which formula does the Azimuth Deviation Loss Calculator use?

The page shows the calculation relationship as Reference orientation = equator-facing (azimuth = 0° in local convention). Review the displayed substituted steps because some tools use additional conditions or unit conversions.

How should I check a Azimuth Deviation Loss Calculator result?

Verify the input values and units first, then compare the result with the displayed calculation steps, assumptions, warnings and any cited reference that applies to your use case.

What are the limitations of the Azimuth Deviation Loss Calculator?

The result depends on the values, units and assumptions entered. Treat it as a calculation aid and use the applicable official document, manufacturer data or qualified professional review when the decision requires one.

Where can I find related tools?

Use the related-tools links on the page or browse the Solar Engineering collection for another calculation method or supporting tool.

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Azimuth Deviation Loss

Annual energy loss vs deviation from true south (N-hem).

Performance

Core inputs only — quick sizing with engineering defaults.

Inputs (SI units)

Site latitude°

Signed: negative = Southern hemisphere.

Array tilt°

Azimuth deviation from equator-facing° (east −, west +)

Signed: negative = east of equator-facing, positive = west of equator-facing.

Results

Annual energy loss vs equator-facing

0 %

Retained annual yield

100 %

Best month relative yield

100 %

Worst month relative yield

100 %

✓ PASS — Deviation within ±30° of equator-facing — typically low impact.

✓ PASS — Estimated annual loss below the 25% threshold that usually triggers redesign.

Solar PV decision support

PV design decision summary

This section organises the existing calculator output into design checks, governing criteria and comparison cases. Core solar formulas and the calculator's original results are unchanged.

Solar PV sizing & array decision support v3 · 2026.08

Explicit checks passed

2 explicit checks passed for the entered values. This does not replace independent verification where the decision is safety-critical, contractual, statutory, financial or medical.

2 pass

Governing criterion

Azimuth deviation from the reference direction

0 %

The existing empirical orientation model converts angular deviation into an annual energy-loss estimate.

Design checks

Solar engineering check 1

pass

✓ PASS — Deviation within ±30° of equator-facing — typically low impact.

Structured directly from this solar calculator's own runtime alert.

Solar engineering check 2

pass

✓ PASS — Estimated annual loss below the 25% threshold that usually triggers redesign.

Structured directly from this solar calculator's own runtime alert.

Next design actions

Engine recommendation 1

Loss estimate is irradiation-weighted using your monthly GHI — treat as an engineering estimate, not a bankable PVsyst run.

Engine recommendation 2

Prefer within ±20–30° of equator-facing wherever the roof/land allows.

Engine recommendation 3

Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.

Primary design output

0 %

Use as a preliminary result and verify the project-specific limits listed below.

Methodology & limit

Decision support is structured from the existing solar calculator engine and the current user inputs. PASS/FAIL is shown only where the engine or entered project criteria support an explicit check. Final PV design still requires site survey, exact module/inverter datasheets, structural/electrical design and applicable statutory approval.

Engineering Recommendations

→Loss estimate is irradiation-weighted using your monthly GHI — treat as an engineering estimate, not a bankable PVsyst run.
→Prefer within ±20–30° of equator-facing wherever the roof/land allows.
→Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.

Detailed Calculation Log

Incidence-angle integration over representative days for each month. Irradiation-weighted using the 12 supplied monthly GHI values.

Save & Load Project

Designs are stored privately in this browser — nothing is uploaded.

Engineering Formula

Reference orientation = equator-facing (azimuth = 0° in local convention)
cosθ = sinδ·sinφ·cosβ − sinδ·cosφ·sinβ·cosγ + cosδ·cosφ·cosβ·cosω + cosδ·sinφ·sinβ·cosγ·cosω + cosδ·sinβ·sinγ·sinω
Representative-day hourly integration of max(0,cosθ) → relative monthly yield vs γ=0
Annual loss% = 1 − (Σ POA(γ) / Σ POA(γ=0))

Small deviations (±20°) cost little (< 5%). East/west facing arrays lose ~15–20% annually vs due south.

Step-by-step Calculation

1.Latitudeφ (signed)28.6°
2.Tiltβ25°
3.Azimuth deviationγ (signed, east −, west +)0°
4.Monthly relative yield rangemin..max over 12 months100% .. 100%
5.Annual energy loss vs equator-facing1 − weighted avg relative yield0 %

How to use this calculator: Azimuth Deviation Loss

Annual energy loss vs deviation from true south (N-hem). The example below is calculated by this page's real engine from the displayed inputs.

1Confirm that the Azimuth Deviation Loss matches the quantity or design check you need.
2Enter Site latitude, Array tilt, and Azimuth deviation from equator-facing using the units printed beside each field.
3Check every value before calculating, especially decimal points and measurement units.
4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.

Input guide and example values

Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.

Input	Example value	Why it matters
Site latitude	28.6 °	Signed: negative = Southern hemisphere.
Array tilt	25 °	Measured or known array tilt used by the calculation engine.
Azimuth deviation from equator-facing	0 ° (east −, west +)	Signed: negative = east of equator-facing, positive = west of equator-facing.
Monthly avg. GHI — Jan	3.4 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Feb	4 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Mar	4.9 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Apr	5.6 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — May	6 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Jun	5.7 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Jul	5 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Aug	4.9 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Sep	4.8 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Oct	4.3 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Nov	3.6 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Dec	3.2 kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Formula inputs & variables for Azimuth Deviation Loss

These are the named quantities used by this calculator. When the source formula does not define a mathematical symbol, OneCalcApp keeps the real input label instead of inventing one.

Variable / input	Unit	Meaning in this calculation
Site latitude	°	Signed: negative = Southern hemisphere.
Array tilt	°	Measured or known array tilt used by the calculation engine.
Azimuth deviation from equator-facing	° (east −, west +)	Signed: negative = east of equator-facing, positive = west of equator-facing.
Monthly avg. GHI — Jan	kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Feb	kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Mar	kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — Apr	kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.
Monthly avg. GHI — May	kWh/m²/day	Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

How the Azimuth Deviation Loss works

The Azimuth Deviation Loss uses Site latitude, Array tilt, Azimuth deviation from equator-facing, Monthly avg. GHI — Jan, Monthly avg. GHI — Feb, Monthly avg. GHI — Mar, Monthly avg. GHI — Apr, Monthly avg. GHI — May, Monthly avg. GHI — Jun, Monthly avg. GHI — Jul, Monthly avg. GHI — Aug, Monthly avg. GHI — Sep, Monthly avg. GHI — Oct, Monthly avg. GHI — Nov, and Monthly avg. GHI — Dec to calculate Annual energy loss vs equator-facing, Retained annual yield, Best month relative yield, and Worst month relative yield. Its engine applies Reference orientation = equator-facing (azimuth = 0° in local convention); the worked values below come from that same live calculation rather than a separately typed example.

With Site latitude 28.6 °, Array tilt 25 °, Azimuth deviation from equator-facing 0 ° (east −, west +), Monthly avg. GHI — Jan 3.4 kWh/m²/day, Monthly avg. GHI — Feb 4 kWh/m²/day, Monthly avg. GHI — Mar 4.9 kWh/m²/day, Monthly avg. GHI — Apr 5.6 kWh/m²/day, Monthly avg. GHI — May 6 kWh/m²/day, Monthly avg. GHI — Jun 5.7 kWh/m²/day, Monthly avg. GHI — Jul 5 kWh/m²/day, Monthly avg. GHI — Aug 4.9 kWh/m²/day, Monthly avg. GHI — Sep 4.8 kWh/m²/day, Monthly avg. GHI — Oct 4.3 kWh/m²/day, Monthly avg. GHI — Nov 3.6 kWh/m²/day, and Monthly avg. GHI — Dec 3.2 kWh/m²/day, the main worked-example result is Annual energy loss vs equator-facing = 0 %.

How each Azimuth Deviation Loss input is used

Site latitude

The Azimuth Deviation Loss worked example uses Site latitude = 28.6 °. This value is passed directly into the calculation, with an allowed minimum -66 and maximum 66. Signed: negative = Southern hemisphere.

Array tilt

The Azimuth Deviation Loss worked example uses Array tilt = 25 °. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 90.

Azimuth deviation from equator-facing

The Azimuth Deviation Loss worked example uses Azimuth deviation from equator-facing = 0 ° (east −, west +). This value is passed directly into the calculation, with an allowed minimum -180 and maximum 180. Signed: negative = east of equator-facing, positive = west of equator-facing.

Monthly avg. GHI — Jan

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Jan = 3.4 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Feb

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Feb = 4 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Mar

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Mar = 4.9 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Apr

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Apr = 5.6 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — May

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — May = 6 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Jun

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Jun = 5.7 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Jul

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Jul = 5 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Aug

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Aug = 4.9 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Sep

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Sep = 4.8 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Oct

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Oct = 4.3 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Nov

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Nov = 3.6 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Monthly avg. GHI — Dec

The Azimuth Deviation Loss worked example uses Monthly avg. GHI — Dec = 3.2 kWh/m²/day. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1500. Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

Azimuth Deviation Loss formulas and result interpretation

Formula 1: relationship used

In the Azimuth Deviation Loss, Reference orientation = equator-facing (azimuth = 0° in local convention). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 2: relationship used

In the Azimuth Deviation Loss, cosθ = sinδ·sinφ·cosβ − sinδ·cosφ·sinβ·cosγ + cosδ·cosφ·cosβ·cosω + cosδ·sinφ·sinβ·cosγ·cosω + cosδ·sinβ·sinγ·sinω. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 3: relationship used

In the Azimuth Deviation Loss, Representative-day hourly integration of max(0,cosθ) → relative monthly yield vs γ=0. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 4: relationship used

In the Azimuth Deviation Loss, Annual loss% = 1 − (Σ POA(γ) / Σ POA(γ=0)). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Annual energy loss vs equator-facing

For the displayed Azimuth Deviation Loss worked example, Annual energy loss vs equator-facing is 0 %. Verify Site latitude, Array tilt, and Azimuth deviation from equator-facing and their units before relying on this output.

Retained annual yield

For the displayed Azimuth Deviation Loss worked example, Retained annual yield is 100 %. Verify Site latitude, Array tilt, and Azimuth deviation from equator-facing and their units before relying on this output.

Best month relative yield

For the displayed Azimuth Deviation Loss worked example, Best month relative yield is 100 %. Verify Site latitude, Array tilt, and Azimuth deviation from equator-facing and their units before relying on this output.

Worst month relative yield

For the displayed Azimuth Deviation Loss worked example, Worst month relative yield is 100 %. Verify Site latitude, Array tilt, and Azimuth deviation from equator-facing and their units before relying on this output.

Azimuth Deviation Loss accuracy, checks and limitations

Azimuth Deviation Loss units check: confirm Site latitude (°), Array tilt (°), Azimuth deviation from equator-facing (° (east −, west +)), Monthly avg. GHI — Jan (kWh/m²/day), Monthly avg. GHI — Feb (kWh/m²/day), Monthly avg. GHI — Mar (kWh/m²/day), Monthly avg. GHI — Apr (kWh/m²/day), Monthly avg. GHI — May (kWh/m²/day), Monthly avg. GHI — Jun (kWh/m²/day), Monthly avg. GHI — Jul (kWh/m²/day), Monthly avg. GHI — Aug (kWh/m²/day), Monthly avg. GHI — Sep (kWh/m²/day), Monthly avg. GHI — Oct (kWh/m²/day), Monthly avg. GHI — Nov (kWh/m²/day), and Monthly avg. GHI — Dec (kWh/m²/day) before calculating.
Azimuth Deviation Loss result check: compare Annual energy loss vs equator-facing, Retained annual yield, Best month relative yield, and Worst month relative yield with the substituted formula steps and the displayed rounding precision.
Azimuth Deviation Loss: Use this result for preliminary design and cross-checking. Confirm the applicable code edition, manufacturer data, site conditions and qualified-engineer approval before final design or installation.

Understanding the result

Read the main result together with supporting checks, assumptions, limits and intermediate values.

For a manual check, repeat the first equation, confirm the units and change one input at a time.

Common mistakes when using Azimuth Deviation Loss

Do not mix units for Site latitude (°), Array tilt (°), Azimuth deviation from equator-facing (° (east −, west +)). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
Do not replace the displayed Reference orientation = equator-facing (azimuth = 0° in local convention) relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
Do not treat Annual energy loss vs equator-facing = 0 % from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.

When the Azimuth Deviation Loss is useful

Azimuth Deviation Loss is designed for cases where Site latitude, Array tilt, Azimuth deviation from equator-facing, Monthly avg. GHI — Jan are known and you need Annual energy loss vs equator-facing, Retained annual yield, Best month relative yield. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.

Use the calculator for the scope described by its inputs and notes. The displayed method is Reference orientation = equator-facing (azimuth = 0° in local convention). If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.

Site latitude and Array tilt: what changes the answer

The worked example uses Site latitude = 28.6 °, Array tilt = 25 °, Azimuth deviation from equator-facing = 0 ° (east −, west +), Monthly avg. GHI — Jan = 3.4 kWh/m²/day. With those values, Annual energy loss vs equator-facing is 0 %. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.

For this calculator, the main input roles are: Site latitude (°): Signed: negative = Southern hemisphere. Array tilt (°): Measured or known array tilt used by the calculation engine. Azimuth deviation from equator-facing (° (east −, west +)): Signed: negative = east of equator-facing, positive = west of equator-facing. Monthly avg. GHI — Jan (kWh/m²/day): Leave all months blank to skip the monthly optimisation and use the latitude-based estimate only.

How to sanity-check a Azimuth Deviation Loss result

Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Annual energy loss vs equator-facing, because it is the first worked-example output shown by the live engine.

Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.

Next logical calculator

Continue with Solar Generation Calculator

Solar Generation Calculator covers the same practical workflow from a related calculation angle, making it a useful cross-check after Azimuth Deviation Loss.

Open Solar Generation Calculator

Standards, source trail and limitations

References show the method used. Check the current local edition, amendments and project specification before a regulated decision.

NREL PVWatts

Design Assumptions

• Fixed tilt near latitude.
• N-hem convention: 0° = due south, +ve = west.

Engineering Tips

◆Prefer south ± 15° whenever roof allows.
◆SW bias favors evening self-consumption tariffs.

Warnings

▲Losses > 25% typically require plant redesign or tracking.

Standards & References

NREL PVWatts

Related Solar Calculators

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Monthly Yield Split

Distribute annual generation across months (India typical).

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Inputs (SI units)

Results

PV design decision summary

Design checks

Next design actions

Engineering Recommendations

Detailed Calculation Log

Save & Load Project

Engineering Formula

Step-by-step Calculation

How to use this calculator: Azimuth Deviation Loss

Input guide and example values

Formula inputs & variables for Azimuth Deviation Loss

How the Azimuth Deviation Loss works

How each Azimuth Deviation Loss input is used

Site latitude

Array tilt

Azimuth deviation from equator-facing

Monthly avg. GHI — Jan

Monthly avg. GHI — Feb

Monthly avg. GHI — Mar

Monthly avg. GHI — Apr

Monthly avg. GHI — May

Monthly avg. GHI — Jun

Monthly avg. GHI — Jul

Monthly avg. GHI — Aug

Monthly avg. GHI — Sep

Monthly avg. GHI — Oct

Monthly avg. GHI — Nov

Monthly avg. GHI — Dec

Azimuth Deviation Loss formulas and result interpretation

Formula 1: relationship used

Formula 2: relationship used

Formula 3: relationship used

Formula 4: relationship used

Annual energy loss vs equator-facing

Retained annual yield

Best month relative yield

Worst month relative yield

Azimuth Deviation Loss accuracy, checks and limitations

Understanding the result

Common mistakes when using Azimuth Deviation Loss

When the Azimuth Deviation Loss is useful

Site latitude and Array tilt: what changes the answer

How to sanity-check a Azimuth Deviation Loss result

Continue with Solar Generation Calculator

Standards, source trail and limitations

Design Assumptions

Engineering Tips

Warnings

Standards & References

Related Solar Calculators

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