In addition to solar cells, a typical photovoltaic (PV) module or solar panel consists of these components:

 

A transparent top surface, usually glass

An encapsulant – usually thin sheets of ethyl vinyl acetate that hold together the top surface, solar cells, and rear surface

A rear layer – a thin polymer sheet, typically Tedlar, that prevents the ingress of water and gases

A frame around the outer edge, typically aluminum.

 

Energy performance ratings

Energy performance ratings for PV modules include the following:

 

Peak watt (Wp)
Measures the maximum power of a module under laboratory conditions of relatively high light level, favorable air mass, and low cell temperature. These conditions are not typical in the real world.

Normal operating cell temperature (NOCT)
Measures a module's nominal operating cell temperature after the module first equilibrates with a specified ambient temperature. It results in a lower watt value than the peak-watt rating, but it is probably more realistic.

AMPM standard
Measures the performance of a solar module under more realistic operating conditions. It considers the whole day rather than "peak" sunshine hours, based on the description of a standard solar global-average day (or a practical global average) in terms of light levels, ambient temperature, and air mass.