Typical Loss Factors
Loss Factors in HelioScope
This table provides typical values for the loss factors in HelioScope energy simulations, and the high-level drivers of the various losses.
|POA Irradiance||+1% to +20%||Depends on tilt of array; one of the rare numbers that will be positive, i.e. an increase. If negative, means the modules are pointed away from the equator.|
|Shaded Irradiance||0 to -10%||Depends on shading in Design. Will come from three sources: row-to-row, obstructions, and horizon files.|
|Reflection||-1% to -5%||Based on reflection of light from shallow angles. Will be larger for lower-tilt arrays, and locations farther from the equator.|
|Soiling||-1% to -5%||Defined in the Condition Set. Can be negative (i.e. to add in gains). Also used to account for snow losses. Default is 2% loss.|
|Output at Irradiance||-1% to -5%|| Accounts for non-linear behavior of module I/V curve under low light (i.e. at 500W/m2, a module is not producing exactly half of rated power). More details available in our Output at Irradiance help doc.
|Output at Temperature|| -3 to -7% for fixed tilt
-6 to -15% for flush mount
| All arrays will have temperature-related losses. Flush-mounted arrays (i.e. residential) don’t get as much ventilation as fixed-tilt array, and therefore run hotter.
|Output at Mismatch||0 to -7%|| Default mismatch assumptions in Condition Set should lead to ~2% mismatch loss. If shading losses, then there will be additional mismatch caused by the shading, approximately equal to the shading losses. If module-level optimization (i.e. microinverters or optimizers), should be zero by default.
|Optimizer Output||0 to -2%||Accounts for efficiency of DC optimizers, if included in Design. Otherwise will be zero.|
|Optimal DC Output||0 to -2%|| Accounts for DC wiring losses between modules and inverter
|Constrained DC Output||0 to -3%||Accounts for clipping losses. Typically over-power clipping can be 1-2% in a healthy design, and up to 4-5% in an aggressive design. Under-voltage can also cause more significant losses (10-30%), but should be able to be addressed by improved design (i.e. string size)|
|Inverter Output||-2% to -7%||Accounts for efficiency of inverter.|
|Energy to Grid||-0.5% to -3%||Accounts for AC losses between inverter and grid connection.|
| Total Performance Ratio
||68% to 88%||Composite of all of the factors above (excluding POA irradiance). Biggest drivers of differences are temperature losses and shading – hotter locations will be on the lower end of the range, cooler locations on the higher end.|