Monocrystalline -  These cells are made from one large silicon crystal.  They are the most efficient (18%) and most expensive solar panels.  Monocrystalline panels cost about $3.50 per watt.

Multicrystalline - These are the most common solar panels on the market.  Each cell is composed of a group of small silicon crystals.  They are about 15% efficient. Some Chinese multicrystalline panels sell for as little as $1.85 per watt.

Amorphous -  These panels use a film of silicon spread over stainless steel.  They are the least expensive and least efficient.  They also degrade about twice as fast as crystalline systems.

Thin Film Laminates:  A new technology borrowed from the computer semiconductor industry allows a thin layer (1 to 10 micrometers ) of monolithic silicon PV to be printed out on a variety of surfaces.  This technology will eventually make building integrated PV more affordable and practical.  Currently thin film PV costs more than crystalline PV and requires twice as much surface area to produce the same number of watts.  Costs are expected to come down dramatically in the next few years and open up a new generation of PV products.  Currently thin film PV are used primarily on large commercial membrane roofs such as warehouses.  

Wire should be sized for less than 2% power loss.  The larger the wire the less line loss.