Answer
Read a solar shade report by checking the site model and three resource metrics: Solar Access measures shading, TOF measures tilt and orientation, and TSRF combines them. Then inspect monthly and roof-plane results, compare the electrical production simulation, and verify any incentive rules separately. A resource percentage alone cannot select an inverter or guarantee output.
Start with the report’s address, design version and data date. A precise-looking percentage can still describe an outdated tree model or a roof plane different from the one in the quote. This guide explains what the report measures and how to turn it into questions for the designer, without treating a sunlight score as a production guarantee.
Understand Solar Access, TOF and TSRF
The Solmetric definitions distinguish orientation from shading. Aurora’s report documentation describes the same resource measures:
| Metric | Comparison | What it tells you |
|---|---|---|
| Solar Access | Shaded resource divided by unshaded resource at the same orientation | The modeled shading effect |
| Tilt and Orientation Factor (TOF) | Unshaded resource at the actual orientation divided by the optimal reference | The orientation effect |
| Total Solar Resource Fraction (TSRF) | Shaded actual resource divided by optimal unshaded reference | Both effects together |
Solar Access of 100% means no shading reduction under that metric; it does not require a south-facing roof. TSRF is a resource ratio, not module conversion efficiency or the percentage of your electricity bill covered by solar. Check the tool’s reference orientation, weather model and aggregation method before comparing reports from different systems.
Worked example: keep percentages consistent
Illustrative inputs, not a measured site: an optimal unshaded surface receives 2,000 kWh/m² over the modeled year. The actual roof without shading receives 1,900 kWh/m²; with shading it receives 1,710 kWh/m².
| Calculation | Result |
|---|---|
| TOF = 1,900 ÷ 2,000 × 100 | 95% |
| Solar Access = 1,710 ÷ 1,900 × 100 | 90% |
| TSRF = 90 × 95 ÷ 100 | 85.5% |
| Direct check = 1,710 ÷ 2,000 × 100 | 85.5% |
The roof’s orientation accounts for one reduction and the obstruction accounts for another. Improving a tree model or removing an obstruction changes the shading assessment; it does not automatically improve TOF. Reorienting panels can affect both quantities and should be modeled again.
Read the monthly chart correctly
The SunEye manual describes monthly bars as the percentage of solar energy available under the site’s shade conditions. Its unshaded case is 100% in every month, not smaller percentage bars merely because days are shorter.
Compare the low-access months with the obstruction model and the monthly production estimate. Check roof equipment, nearby buildings and tree geometry; distinguish evergreen coverage from any leaf-season assumptions actually supported by the model. Do not infer the tree species from the chart alone.
An annual percentage is a resource-weighted result rather than necessarily the arithmetic mean of twelve bars. Original illustrative check: two periods with unshaded resources of 100 and 300 units and access values of 50% and 100% have combined access of (50 + 300) ÷ (100 + 300) = 87.5%, rather than 75%. Obtain the report’s actual weighting and time basis.
Inspect each roof plane and the underlying model
HelioScope’s shade-report documentation describes module results summarized by field segment. A system headline can conceal a weaker area, so ask for the breakdown used in the proposal.
Use this review checklist:
- Confirm which proposed modules and roof planes are included.
- Check tilt, azimuth convention, obstruction heights and imagery/survey dates.
- Locate the cause of weaker access values rather than assuming every low score means a tree.
- Ask how near shading, distant horizon and inter-row shading are represented.
- Record any planned mitigation separately from the current site condition.
- Request an updated report when the installed layout or confirmed site geometry changes.
A zero value warrants investigation of both the modeled condition and data quality. It is not automatically a software error: the SunEye manual explicitly includes a fully shaded zero-access case.
Separate sunlight losses from electrical production
Sandia’s PVPMC array-model explanation distinguishes irradiance conditions from electrical mismatch. Modules in series share current, but a shade report’s annual resource value does not by itself describe the array’s full current-voltage behavior.
The PVsyst electrical-shading presentation hosted by PVPMC explains that optimizer effectiveness depends on the shading, layout and current/voltage limits. Compare actual electrical simulations instead of prescribing string inverters above 85% TSRF and microinverters below 70%.
Optimizers do not restore intercepted sunlight. Neither an access percentage nor a monthly shading average establishes start voltage, string safety or MPPT compatibility; those require the equipment documents and electrical design. See MPPT explained for the separate operating concept.
Aurora’s loss-diagram documentation separates irradiance losses from DC, AC and other losses. Ask whether the production model includes shading once, and how it treats mismatch, temperature, clipping and availability. Multiplying an already shaded production forecast by Solar Access again would count that reduction twice.
Check acceptance and economics separately
For a lender or incentive application, record the administrator, current document version, required metric, approved method, averaging rule and verification requirements. This guide does not certify current programme thresholds or tool acceptance. Historical validation studies also do not provide a universal accuracy guarantee for every tool, location or tree-heavy site.
Compare layout alternatives using their modeled annual and monthly AC energy, installation cost and explicit financial assumptions. A lower TSRF does not automatically make a project uneconomic; a higher TSRF does not guarantee a rebate or payback.
A clear explanation for the customer
“Solar Access describes modeled shading on this roof. TOF describes orientation, and TSRF combines both. The production forecast also accounts for the equipment and other losses. Here is the weaker roof section, its obstruction, and the change we modeled. We will confirm incentive eligibility separately.”
Keep the report, production model and quotation on the same design revision. If evaluating SurgePV’s shading workflow, bring a representative report and ask which analysis and export outputs are available. Discuss the workflow in a demo before assuming a required lender format is supported.
Frequently Asked Questions
What is TSRF in solar?
Total Solar Resource Fraction combines shading and tilt/orientation relative to an unshaded, optimally oriented reference surface in the model. When the inputs are percentages, TSRF (%) = Solar Access (%) × TOF (%) ÷ 100.
What is a good TSRF percentage?
A higher TSRF indicates more modeled solar resource relative to the reference. There is no universal percentage that guarantees an economic project, selects an inverter, or establishes incentive eligibility. Evaluate production, cost, tariff assumptions and the current programme rules.
Do optimizers increase Solar Access?
Optimizers can mitigate some electrical mismatch losses, subject to the equipment and layout. They do not remove a tree shadow or change the geometric sunlight resource measured by Solar Access.
Does low winter Solar Access just mean shorter days?
No. Monthly Solar Access compares shaded with unshaded resource for the same period. Shorter days reduce the absolute available energy, while a lower access percentage indicates a shading effect in the model.
What makes a shade report bankable?
Acceptance depends on the particular lender or incentive administrator, its current rules and the evidence supplied. A software label or historical acceptance claim does not establish acceptance for your project.
Where this fits
This article is part of SurgePV's Solar Design hub, which works through the topic from first principles to the decisions a project team actually has to make.
