Solar Shading Loss Calculator

Model shading losses for rooftops, canopies, and fields. See kWh, revenue, and carbon changes instantly. Adjust geometry, hours, and electronics to recover energy fast.

Calculator inputs

Nameplate DC size of the PV system.
Local annual production per installed kW.
Choose a direct percent or a modeled estimate.
Use a measured or simulated annual percent loss.
Used to estimate annual value change.
Percent of modules affected during shading.
How much the sun component drops when shaded.
Average hours per day with shading present.
Seasonal shading often affects fewer days.
Higher diffuse reduces shading sensitivity.
Mitigation varies by architecture.
Used to estimate emissions linked to lost energy.
Fields marked with * are recommended for accurate results.

Formula used

Baseline annual energy
Baseline (kWh/yr) = System size (kW) × Specific yield (kWh/kW·yr)
If you enable custom baseline, the calculator uses your baseline value instead.
Percent method
Lost energy = Baseline × (Shading loss % ÷ 100)
Net energy = Baseline − Lost energy
Time and impact method
Loss % = 100 × BeamFraction × TimeFraction × ArrayFraction × IrradianceReduction × Mitigation
  • BeamFraction = 1 − (DiffuseFraction ÷ 100)
  • TimeFraction = (ShadeHours ÷ 24) × (ShadeDays ÷ 365)
  • ArrayFraction = ShadedFraction ÷ 100
  • IrradianceReduction = IrradianceReduction% ÷ 100
  • Mitigation is lower for module-level electronics.
This simplified model is intended for early design comparisons.
Cost and emissions
Value lost = Lost energy × Electricity rate
CO₂ tied to lost energy = Lost energy × Emission factor

How to use this calculator

  1. Enter your system size and expected specific yield.
  2. Pick the shading method that matches your data quality.
  3. If you know annual shading loss, use the percent method.
  4. For planning, switch to time and impact inputs.
  5. Set your electricity rate and grid emission factor.
  6. Click calculate to view results above the form.
  7. Download CSV for records and PDF for reports.

Shading loss as a design constraint

Shading reduces irradiance on modules and can trigger mismatch losses across strings. Even small obstructions such as parapets, vents, and nearby trees may create recurring energy deficits. Quantifying loss early supports better row spacing, setback decisions, and electrical zoning that protect annual production targets during early planning.

Baseline energy and loss translation

The calculator converts a loss percentage into lost kilowatt-hours by multiplying baseline annual energy by the loss fraction. Baseline can be estimated from system size and site-specific yield, or entered from measured production. This makes results comparable across rooftops, carports, and ground-mount arrays. For upgrades, use last-year kWh to anchor estimates to real performance.

Time and impact modeling inputs

When detailed shading observations exist, the time and impact method estimates loss using shaded array fraction, irradiance reduction during shade, shading hours per day, and shaded days per year. Diffuse fraction reduces sensitivity because diffuse light is less directional. The method is intentionally conservative for feasibility checks. Use seasonal shade days to reflect winter sun angles and deciduous canopies.

Electrical architecture mitigation

Power electronics influence how localized shade propagates into whole-string losses. Multi-MPPT inverters can isolate differently oriented planes, while module-level devices can limit mismatch to only shaded modules. Use the electronics selector to compare mitigation scenarios and quantify potential recovered energy. Pair the comparison with layout changes to target the highest-loss hours.

Cost and carbon interpretation for projects

Annual value loss uses your electricity rate to translate energy deficits into monetary impact, supporting payback and contract discussions. The emissions factor estimates carbon tied to the lost clean generation, useful for ESG reporting. Compare options such as pruning, relocating equipment, or increasing setback to reduce recurring losses. Document assumptions in commissioning notes so stakeholders understand the uncertainty range.

FAQs

What does shading loss percentage represent?

It is the share of annual energy that the system does not produce due to shading and related mismatch effects. It is expressed as a percent of baseline annual energy.

When should I use the percent method versus time and impact?

Use percent when you already have an annual loss estimate from monitoring or simulation. Use time and impact when you only know how often shading occurs and how severe it is.

How do module optimizers or microinverters change results?

Module-level electronics reduce mismatch propagation, so shade on one module has less impact on the rest of the array. The calculator applies a mitigation factor to reflect this improvement.

Why is diffuse fraction included in the detailed method?

Diffuse light arrives from many angles and is less blocked by narrow obstructions. A higher diffuse fraction lowers the beam component and reduces modeled sensitivity to shading hours.

Can I enter measured annual production as the baseline?

Yes. Enable the custom baseline option and enter your annual kWh. This anchors loss estimates to actual site performance, which is useful for retrofits and diagnostics.

Is the cost output a bill savings guarantee?

No. It is an estimate based on your provided electricity rate and net-metering assumptions. Use it for planning comparisons, and confirm project economics with your tariff and contract terms.

Example data table

Scenario System (kW) Yield (kWh/kW·yr) Method Loss (%) Lost (kWh/yr) Net (kWh/yr)
Light chimney shade 6 1450 Percent 4.5 392 8,308
Tree shade mornings 10 1500 Percent 8.0 1,200 13,800
Winter horizon obstruction 12 1600 Time & impact 3.2 614 18,586
Example values are illustrative and not site-specific.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.