Source: solarcalculator
There are several factors that affect the panel output and efficiency of a solar panel. All of these factors must be considered when calculating solar power at any given location.
Manfacturer’s output tolerance
Most solar panels have an output tolerance +/- 3%, which means that the manufacturers panel will perform within 3% of its Watts rating.
The effect of dirt on solar panels
Dirt and grime also affect the efficiency of a solar panel. This varies from panel to panel, however, it’s best to factor in a loss of performance. In all of our calculations, we equate the loss of efficiency due to dirt and grime to be 5%. If you were to clean your panels regularly, they would perform better.
Temperature derating
Solar panels are affected by temperature. The hotter the panels get, the less efficient they become. We cover this topic in great detail here, but the short of it is: the temperature coefficient, ambient temperature, as well as the type of installation all affect the efficiency of the panel and therefore solar panel output.
Roof tilt and orientation
The direction that solar panels face, and the angle that they are mounted, also have an affect on the output of the panel. If they are not positioned at the optimum angle and direction, then the panels will not produce rated output for that location. This is a must when accurately calculating solar output.
Inverter efficiency
The inverter converts Direct Current (DC) into Alternate Current (AC), so that the energy produced by solar panels can be used to power your home’s electricity. This process is not 100% efficient. Whilst inverter efficiency technology is improving, it can still account for as much as an 8% loss in efficiency. We allow for an average of 5% in all of our calculations.
Battery inverter efficiency
If you have a hybrid system with a solar battery, your battery will not operate at its rated Wattage. Inverter efficiency for batteries is in the realm of 92%, representing an 8% loss.
DC cable loss
There may be a small voltage drop between the solar panel system and the inverter, this can account for efficiency losses of around 1-2%.
AC cable loss
Likewise, connection between the inverter and the electricity switchboard of the property, may experience a drop in voltage leading to a small loss in the efficiency of the system.
When accurately calculating solar panel output for a given location, all of these factors should be accounted for. All of our calculators that ask for your postcode factor in the affect of tilt and orientation, and all of the solar panel efficiency factors.
