Solar Irradiance Calculator
Estimate solar irradiance, daily Peak Sun Hours (PSH), and Plane-of-Array radiant energy based on your latitude and tilt angle. Plan efficient solar arrays and optimize clean-energy generation.
Solar Irradiance Calculator
Determine Global Horizontal Irradiance (GHI), Plane-of-Array insolation, optimum seasonal tilt gain, and thermal efficiency losses for PV arrays.
Solar Irradiance Calculator — Peak Sun Hours, Tilt & POA Gain: Estimate solar irradiance, daily Peak Sun Hours (PSH), and Plane-of-Array (POA) insolation based on latitude and tilt angle. Plan efficient solar arrays.
How to Use the Solar Irradiance Calculator
Choose Geographic Tier or Enter GHI
Select your regional solar resource tier (from Desert Southwest 6.2 PSH to Pacific Northwest 3.5 PSH) or input custom meteorological Global Horizontal Irradiance data.
Specify Latitude and Module Tilt Angle
Enter your project latitude and the fixed pitch angle of your roof or ground-mount solar racking to calculate Plane-of-Array (POA) geometric solar gain.
Enter Ambient Temperature & Panel Coefficient
Provide peak summer ambient air temperature and your photovoltaic panel’s Pmax temperature coefficient (typically -0.30% to -0.38% per °C for monocrystalline silicon).
Analyze Effective Yield & System Performance Ratio
Examine plane-of-array insolation, operating cell temperature, thermal efficiency derate, total daily/annual kilowatt-hour generation, and specific energy yield.
Comprehensive Guide: Solar Irradiance Calculator
Solar irradiance quantifies the electromagnetic power per unit area delivered by sunlight onto a surface, conventionally expressed in watts per square meter (W/m²), while cumulative solar insolation measures total radiant energy received over time, expressed in kilowatt-hours per square meter per day (kWh/m²/day). In photovoltaic engineering, one Peak Sun Hour (PSH) is defined as the equivalent duration in hours that the sun would need to shine at standard test conditions (STC) irradiance of 1,000 W/m² to match the total daily radiant energy captured.
A fundamental distinction in solar engineering lies between Global Horizontal Irradiance (GHI) and Plane-of-Array (POA) irradiance. GHI measures total solar radiation hitting an un-tilted flat horizontal surface, incorporating direct beam radiation (Direct Normal Irradiance, or DNI) and scattered ambient atmospheric radiation (Diffuse Horizontal Irradiance, or DHI). Tilting a photovoltaic panel toward the equator allows the module to intercept incoming direct beam sunlight at a much tighter, perpendicular angle of incidence, capturing up to 8% to 15% more annual kilowatt-hours than a flat horizontal installation.
Photovoltaic efficiency is strongly temperature-dependent. Photovoltaic solar panels are laboratory-tested at Standard Test Conditions (STC) with a cell temperature of 25°C (77°F). In real-world summer sunlight, dark photovoltaic modules absorb significant infrared thermal radiation, heating operating cells to 25°C to 35°C above ambient air temperatures. Because the semiconductor bandgap of silicon narrows at elevated temperatures, solar cell voltage drops significantly, causing panel power output to decrease by 0.30% to 0.40% for every single degree Celsius above 25°C.
Understanding realistic system Performance Ratio (PR) is critical for commercial and residential production guarantees. While raw solar irradiance indicates available fuel from the sun, the end-to-end AC energy delivered to the electrical service panel reflects multiple compounding efficiency losses: module temperature derating (8% to 14%), DC string resistance (1% to 2%), inverter DC-to-AC conversion loss (2% to 4%), glass soiling and dust (2% to 5%), and module manufacturing nameplate tolerance. Modern utility and residential solar installations achieve overall annual Performance Ratios ranging between 78% and 84%.
Key Features & Capabilities
Plane-of-Array (POA) Geometry Modeling
Computes geometric cosine angle enhancement for tilted arrays over horizontal Global Horizontal Irradiance (GHI).
NOCT Cell Temperature Simulation
Estimates real-world photovoltaic wafer thermal equilibrium using ambient conditions and Nominal Operating Cell Temperature models.
Temperature Derating Pmax Coefficient
Calculates power loss from thermal voltage degradation using manufacturer monocrystalline and bifacial silicon coefficients.
Optimum Seasonal Tilt Recommendations
Outputs optimal fixed year-round pitch as well as bi-annual summer and winter adjustable racking angles for your latitude.
System Performance Ratio (PR) Calculation
Translates raw solar insolation into net AC energy output accounting for inverter efficiency, cabling, and soiling.
Specific Energy Yield (kWh/kWp)
Provides standard industry metrics to benchmark project productivity against regional NREL PVWatts utility averages.
Frequently Asked Questions
Solar irradiance is the instantaneous rate of radiant power arriving from the sun, measured in watts per square meter (W/m²). Solar insolation is the accumulated radiant energy received over a specific time window (such as a full day), measured in kilowatt-hours per square meter per day (kWh/m²/day), which directly equals Peak Sun Hours (PSH).
Contrary to intuition, solar panels produce less electricity when they get very hot. Solar cells are rated at 25°C (77°F). When dark panels sit in hot summer sunshine, cell temperatures often reach 55°C to 65°C. With a typical temperature coefficient of -0.35%/°C, an operating cell at 65°C experiences a 14% reduction in peak wattage.
For fixed year-round systems, the optimal tilt angle is roughly equal to your site latitude (or latitude multiplied by 0.9). For arrays with seasonal adjustable mounts, tilt at latitude minus 15° in summer (to catch the high midday sun) and latitude plus 15° in winter (to face low horizon sun).
Plane-of-Array (POA) irradiance is the sum of direct beam, diffuse sky, and ground-reflected radiation arriving perpendicular to the tilted face of the solar module. It represents the actual sunlight available for the solar cells to convert into electricity.
A well-engineered grid-tied photovoltaic system typically achieves an annual Performance Ratio between 78% and 85%. This ratio represents the actual AC energy exported divided by the theoretical energy the system would produce if operating continuously at STC rating under the measured sunlight.