The system loss diagram gives you a complete breakdown of how energy moves through your solar design — from the moment sunlight hits your modules to the final AC energy delivered to the home. Every stage in the diagram shows what percentage of energy is lost and why, so you can identify which losses are within your control and which are simply physical or environmental.
| 📝 Note: Admins can edit system loss defaults across their tenant, and users are able to modify some system loss percentages with each design. For more information, see System Losses. |
You can access the system loss diagram from the simulation panel > Advanced dropdown after running a performance simulation on any design in Design Mode.
Irradiance losses
This section shows how much usable irradiance actually reaches your modules after accounting for their tilt, orientation, and environmental conditions.
Irradiance at optimal tilt/orientation
This is the starting point of the loss diagram — the maximum annual irradiance that could fall on the modules if they were perfectly tilted and oriented for your site's location.
Tilt
This loss represents irradiance not captured because your modules aren't at the optimal tilt or azimuth for the site. Modules on a flat roof, for example, will show a higher loss here than modules tilted at 20–30°, depending on the location.
Horizon
This loss accounts for irradiance blocked by distant terrain – hills, mountains, ridgelines, and other far-field features that cast shade on a site from a distance. Aurora automatically builds a 360° horizon profile from elevation data when you run a simulation, so no manual modeling is required.
The loss is under 1% for most flat-area sites, but can be significantly higher for sites in valleys, canyons, or on hillsides.
For more detail on horizon shading, see this blog article.
Shade
This is the irradiance lost to shading from trees, obstructions, walls, adjacent rooflines, and other modules. Aurora's integrated shading engine calculates this value directly using your 3D model. With LIDAR Shading enabled, this value will factor in the shading from surrounding LIDAR.
If you run a simulation with the shading engine disabled, the shade loss shown here reflects the manual shade derate you set in your system loss settings.
Soiling
This loss accounts for dirt, sand, dust, or other debris on the modules. The value applied is the soiling loss defined in your system loss settings — you can set it as a single annual value or vary it by month.
Snow
This loss accounts for snow covering modules during winter months. Like soiling, it's applied using the value (or monthly values) from your system loss settings.
Incidence Angle
Irradiance that strikes a solar panel at an angle — rather than straight on — experiences optical losses as it passes through the module cover. This row quantifies those losses. Aurora's IAM model is based on Snell's law and Bouguer's law.
Tip: IAM losses are typically small (under 3%) for well-oriented south-facing arrays but can be more significant for east- or west-facing configurations.
DC losses
This section covers all electrical losses that occur on the DC side of the system — between the modules and the inverter inputs.
Energy after PV conversion
This is the starting point for the DC section. It represents how much energy the design could theoretically produce given the incident irradiance, module efficiency, and module area:
E = S × Σ(ηA)
Where S is the irradiance (kWh/m²), η is the module's peak efficiency at STC, and A is the module area (m²).
Environmental conditions
This is the largest DC loss for most designs. It represents energy lost because modules operate across varying irradiance and temperature conditions throughout the year — not at the ideal STC conditions their ratings assume.
Aurora runs a full circuit simulation for each hour, adjusting the equivalent circuit parameters of every module (or cell string, for submodule simulation) based on real-time irradiance and temperature.
Related: Aurora Simulation Engine · Submodule (Cell String)-Level Simulation
Module Rating
This is the same nameplate rating loss configured in your system loss settings. It accounts for the possibility that a module's STC rating slightly overstates its real-world power output.
Most modern panels have a positive power tolerance, meaning they typically meet or slightly exceed their rated output — so this loss is often small.
Degradation
Light-induced degradation (LID) is a physical phenomenon where the electrical characteristics of crystalline silicon cells shift after their first exposure to light. The change happens quickly — within the first few hours of operation — but it's permanent, so Aurora models it as a fixed loss factor.
The value applied here matches the LID setting in your system loss settings.
Connections
This is the resistive loss caused by internal wiring and soldering connections inside the solar panels. These connections add electrical resistance, which reduces power output.
Mismatch
No two modules from the same production run are perfectly identical. Small variations in electrical parameters across modules — even within the same string — cause slight energy losses. This row captures those manufacturing tolerance effects.
Note: Mismatch losses are not applied to designs using microinverters or DC optimizers, because module-level power electronics isolate each module from the rest of the string.
DC wiring
This is the resistive loss in the cables connecting modules together within strings. Longer wire runs or undersized conductors will increase this loss.
AC losses
This section covers all losses on the output side of the inverter.
DC/AC conversion
This is the efficiency loss of the inverters in your design. No inverter converts DC power to AC at 100% efficiency — most operate at 96–98%, though the exact value varies with input power and voltage.
Because Aurora models the full inverter efficiency curve (when test data is available), the loss shown here reflects real operating conditions across the year — not just the nameplate efficiency. A high DC/AC conversion loss can indicate that the array is significantly undersized relative to the inverter's nameplate rating.
Inverter clipping
Clipping occurs when the array produces more DC power than the inverter can handle. When that happens, the inverter caps its output at its nameplate AC rating, and the excess DC energy is lost.
If clipping loss is significant, Aurora also flags it in the simulation warnings. If inverter clipping is disabled in your simulation settings, this row will show 0%.
Related: What is Inverter Clipping?
Other losses
These losses are applied to the final AC energy output and represent miscellaneous factors that affect annual production.
Age
This is the loss due to module degradation over time. It matches the age (degradation) loss defined in your system loss settings.
System availability
This represents energy lost when the system is offline — due to planned maintenance, grid outages, or other downtime. It matches the system availability setting in your system loss settings.
Other
A catch-all for any additional loss factor you want to account for that doesn't fit the categories above. The value comes from the "Other" field in your system loss settings.