PV system losses

A detailed breakdown of your PV system losses is provided on the PV system losses page. For better data analysis, the page is further categorized into yearly and monthly losses, respectively.

Note: We use different methods and models to calculate the losses, and the full breakdown of the loss chain is described here.

The yearly losses

Yearly energy conversion and related losses table

This table is available for both yearly and monthly losses and breaks down how incoming solar energy is reduced by various losses throughout the PV system:

• Input and optical losses: Shows the initial irradiation values and stepwise reductions from shading, soiling, angular, and spectral effects, on both the front and rear sides of the modules (if applicable).

• Conversion losses: Details the loss when converting irradiation to DC electricity in the modules.

• Electrical losses: Lists further reductions from inverters, cables, transformers, auxiliary systems, and unavailability (including snow).

Each loss is quantified:

• Relative to previous: Shows the percentage drop at each stage compared to the immediately preceding value.

• Relative to input: Indicates the loss as a percentage of the original input energy.

• Cumulative performance ratio: Tracks overall system efficiency after each loss, ending with the final value (67.4%), representing the portion of initial solar energy delivered as usable electricity.

The loss diagram

The Loss diagram offers a visual presentation of your system’s cumulative energy losses (solar and electrical). You can read more about how we calculate these losses here.  

Note: Each additional loss displayed is calculated from the previous cumulative loss value rather than the initial total power value. As losses accumulate over time, each subsequent loss is discounted from the remaining power output after previous losses have already been accounted for.

The monthly losses

The monthly losses are visualized in the breakdown of the energy losses chart, which depicts the percentile of individual loss values and their total accumulation every month.

You can toggle the visibility of each loss by clicking its name in the chart legend. Hovering over the value highlights it on the chart, showing its actual values per month along with the total for the year.

Important: The breakdown of losses shows absolute loss values (non-cumulative).

Monthly energy conversion and related losses table

This table details monthly energy losses throughout the PV system, starting from the initial solar input and tracking reductions at each stage:

• Energy input: Shows monthly values for global horizontal irradiation and global tilted irradiation (front and rear sides), both before and after shading.

• Optical losses: Lists monthly percentage losses from shading, soiling, angular, and spectral effects for both module sides.

• Conversion losses: Displays the percentage loss when converting irradiation to DC electricity in the modules each month.

• Electrical losses: Breaks down monthly losses from inverters, DC/AC conversion, cables, transformers, and auxiliary systems.

• Unavailability losses: Shows monthly internal, external, and snow-related downtime losses.

The dropdown menu in the top right lets you choose how losses are displayed:

• Losses in % of GTI (global tilted irradiation) without shading.

• Losses in % difference from the previous step.

• Losses in kWh/m² or kWh/kWp difference from the previous step.

How we calculate the losses

The calculation of losses involves a detailed assessment of various factors that reduce the overall efficiency and energy output of the system. For better understanding, here is a short explanation of each loss included in the diagram:

• Shading Losses: Occur due to partial or complete shading of solar panels when obstructions block solar irradiance from reaching them.

• Soiling Losses: Caused by accumulation of dust and dirt on solar panel surfaces.

• Angular Losses: Result from sunlight incidence angles on solar panels.

• Spectral Losses: Reflect changes in the solar spectrum as light travels through the atmosphere.

• Conversion Losses: Arise during the conversion of sunlight into electrical energy within PV cells.

• DC Losses: This happens due to resistance in cables before inverter conversion.

• Inverter (Power Limitation) Losses: Occur when generated power exceeds inverter capacity.

• Inverter (DC/AC Conversion) Losses: Result from inefficiencies during DC to AC conversion.

• Auxiliary Losses: Come from self-consumption by auxiliary equipment.

• AC Cable Losses (LV): Occur due to resistance in low-voltage cables as current flows from the inverter.

• TR Losses (LV/MV): Losses caused by transformation from low to medium voltages.

• AC Cable Losses (MV): Occur in medium-voltage cables during longer distance transmission.

• TR Losses (MV/HV): Losses caused by transformation from medium to high voltages (if power transformer is used).

• AC Cable Losses (HV): Occur in high-voltage cables connecting the power transformer (if used) to the grid.

• Internal Unavailability Losses: Caused by maintenance or failures of internal components.

• External Unavailability Losses: These are caused by external factors like grid outages or regulatory shutdowns.

More details on losses and how they are calculated are described in the Solargis Evaluate simulation chain document.