Quick answer
Creation of a color-coded solar-radiation map with defined quantity, units, time period, reference and geometry/weather/model inputs; radiation values do not alone establish electrical yield.
Answer: Irradiance heat mapping represents modeled solar radiation across a roof or site using a color scale. A map may show instantaneous irradiance, accumulated irradiation over a stated period or a derived solar-access ratio. Its meaning depends on the quantity, units, reference and model inputs. The overlay supports layout assessment but does not by itself establish electrical yield, structural suitability or an accuracy guarantee.
Specify the output before generating the map
Define the surface, quantity and time period first. The PVsyst irradiation-model documentation distinguishes irradiance, expressed in W/m², from accumulated irradiation, expressed in kWh/m². It also describes decomposition, transposition to the PV plane and shading/optical modeling stages.
| Output | Meaning and units |
|---|---|
| Instantaneous irradiance | Solar power per surface area at the selected instant, W/m² |
| Period irradiation | Solar energy per surface area over the defined period, kWh/m² |
| Solar access | Ratio to the specified matching unshaded reference, % |
| Shadow state | Geometry-based shadow at a selected time, not annual energy |
An annual map described casually as an “irradiance map” may actually display annual irradiation. Check the exported units and model definition. A radiation map is also different from a thermal image measuring apparent surface temperature; the word “heat” describes the visualization, not a measured roof temperature.
Build a traceable calculation workflow
- Define geometry: establish roof planes, orientation, heights and obstructions from imagery, LiDAR, survey or manual inputs. Record source dates and known exclusions.
- Define the solar/weather basis: specify coordinates, time handling, weather period and the radiation inputs available. Sun position alone does not establish weather-adjusted solar energy.
- Set the surface calculation: use the appropriate orientation and radiation components. State whether shading, sky obstruction, reflected radiation and optical effects are included.
- Choose spatial and time resolution: verify how cells or sample points represent narrow obstructions and rapidly changing shadows. Finer sampling cannot fix inaccurate geometry.
- Integrate for the requested period: accumulate power-density values with their time intervals rather than summing arbitrary displayed samples.
- Export the map and evidence: retain numeric values, legend, units, period, surface/reference definition, model revision and software version.
This is a general workflow. Exact engine methods and supported inputs differ, and no automatic satellite-to-model capability is assumed for SurgePV or another platform.
Irradiance-to-irradiation arithmetic
For a hypothetical cell with constant modeled irradiance of 600 W/m² over two hours:
600 W/m² × 2 h = 1,200 Wh/m² = 1.2 kWh/m²
For variable inputs, sum each interval’s average irradiance multiplied by its duration using consistent units. An hourly, subhourly or leap-year model needs its actual intervals; not every map is generated from precisely 8,760 equal frames. Missing intervals must be handled explicitly.
The result is incident solar energy per area, not panel electricity. Converting to delivered electrical energy requires the relevant module, operating-condition, electrical configuration, inverter and loss models. Do not multiply by a vaguely named “system losses” percentage without defining whether it is a loss or a retained fraction and avoiding double-counting effects already modeled.
Solar access needs a matching reference
Aurora’s current solar-access documentation defines the ratio of incident solar energy with shading to incident energy without shading and explains its limits for performance modeling.
Use the same location, surface orientation, weather period and other relevant assumptions, changing the shading condition. A roof’s best-colored zone is not automatically the correct unshaded denominator. Record the tool’s treatment of direct, diffuse and reflected components.
As a hypothetical example, shaded irradiation of 1,200 kWh/m² against a matching unshaded 1,500 kWh/m² gives 1,200 / 1,500 × 100 = 80% solar access. The 20% irradiation deficit does not establish a 20% AC-energy loss. Partial shading, module behavior and electrical connections can change the electrical effect.
Validation and practical use
Compare the model with current site evidence: roof form, obstructions, vegetation assumptions and coordinate/orientation settings. Retain the proposed module overlay so a surface-grid average is not silently substituted for actual module exposure. Changes to trees, buildings or equipment require review of affected geometry and outputs.
Use heat map analysis for interpretation and variant comparisons. Colors and scales are display choices; include the legend and use comparable numeric scales. Evaluate seasonal/hourly results where loads or time-of-use value matter, without claiming that one universal color or solar-access threshold decides every layout.
Designers should use the map to identify candidate zones and then evaluate actual electrical layouts. Installers should flag site discrepancies. Sales teams should explain what is simulated and what remains unverified; a graphic does not demonstrate a guaranteed yield uplift, customer close-rate improvement or a measured accuracy percentage.
For a product evaluation, review the shading workflow and request a demonstration of the required inputs, mapped quantities and exports. Confirm actual capabilities and site-validation needs before promising an automated result.
Frequently asked questions
Is an annual map measured in W/m²?
An accumulated annual solar-energy map normally uses energy per area, such as kWh/m² for the year. W/m² describes irradiance at an instant or an explicitly defined average.
Does the map measure roof temperature?
No. A solar-radiation color overlay is different from thermal imaging. Check the mapped quantity rather than infer temperature from “heat map.”
Does 80% solar access mean 80% electrical output?
Not necessarily. The ratio concerns incident solar energy against a defined reference; electrical output also depends on the actual system and loss modeling.
Can the map replace site verification?
It can support preliminary assessment, but it does not establish roof condition, structural capacity, electrical suitability or that all obstructions are current. Validate the inputs and follow the project’s review requirements.
Related Glossary Terms
About the Contributors
Co-Founder · SurgePV
Akash Hirpara is identified by SurgePV as a company co-founder. His SurgePV author page lists only role information that can be tied to the public profile below; education, certifications, project totals, financial results, speaking engagements, and media appearances are not asserted without retained evidence.
Editorial contributor · SurgePV
Rainer Neumann is credited as an editorial contributor on SurgePV content. This profile does not assert engineering credentials, project totals, software-testing experience, education, speaking engagements, or media citations because independent verification evidence is not retained in the publication record.
