Solar Cell Efficiency
STC Standard Test Conditions: are the basis for comparing optimum output of solar cells aka apples to apples as a way of comparing things that can reasonably be compared.
This optimum output is the ratio of the electrical output of a solar cell to the incident energy in the form of sunlight.
STC Standard Test Conditions are as follows:
Temperature of 77 °F
Irradiance is the measure of solar energy per 1000 Watts per 10.76391ft² generally it is referred to as watts per meter squared.
Real Life Efficiencies
There are a number of things that will adversely affect efficiency in real life situations.
Azimuth relative to the placement of your solar cells, south or 180 is generally the best.
Angle of placement with 0 degrees being vertical and 90 degrees horizontal and 41 degrees is considered the optimum angle.
The temperature, as cells get hotter their efficiency goes down.
Dust on your cells will block the sunlight from getting through.
Obstructions such as clouds, birds or branches will also adversely affect your efficiency.
Your inverter system and how your solar cells are connected can make a big difference on the overall systems energy output.
Solar Panels product DC current which is what is used by cars, laptops in general battery powered products.
To be able to use it in your home or building you need to convert it to AC current.
To do this you have two options
Pros: Lower initial price and simpler to install.
Cons: If you have a problem with one panel it could be as simple as a cloud or branch covering one panel, it can affect the performance of all panels in the system while making it more difficult to trouble shoot a system problem.
Pros: Each panels power is collected independently of other panels in the system allowing each panel to generate optimum energy out put even if one is adversely affected for some reason.
If there is a problem with one unit it is easier to pinpoint the problem and fix it.
Overall it will produce more energy per system.
Cons: More expensive as each panel requires a micro inverter and also requires a longer installation time.