Pre-Module Losses

Tolerance of rated power

Consider that the module does not deliver the power as stated in the data sheet. Manufacturers provide a tolerance, often up to 5%.

Shadows

Shadows may be caused by trees, chimneys etc. Depending on the stringing of the cells, even partial shading may have a significant effect.

Dirt

Losses due to dirt up to 4% in temperate regions with some frequent rain. Up to 25% in arid regions with only seasonal rain and dust.

Snow

Dependent on location and maintenance effort.

Reflection

Reflection losses increase with the angle of incidence. Also, this effect is less pronounced in locations with a large proportion of diffuse light, i.e. clouds.

Module Losses

Conversion

The nominal efficiency is given by the manufacturer for standard conditions.

Thermal losses

With increasing temperatures, conversion losses increase. These losses depend on irradiance (i.e. location), mounting method (glass, thermal properties of materials), and wind speeds. A very rough estimate is ~8%

System Losses ~ 14%

Wiring

Any cables have some resistance and therefore more losses.

MPP

Ability of the MPP tracker in inverters to consistently find the maximum power point.

Inverter

Inverter efficiency

Mis-sized inverter

If the inverter is undersized, power is clipped for high intensity light. If it is oversized, the inverter’s efficiency will be too low for low intensity light.

Transformer

Transformer losses, in case where electricity has to be connected to a high-voltage grid( 11 KV and above ).

Operation & Maintenance

Downtime

Downtime for maintenance is usually very low for photovoltaic systems.