There are three basic types of PV Cells which make up a Solar Panel.
	Single Crystal: (monocrystalline) Each cell is made of a single crystal of silicone. Our best modules are made with this type of cell. They are the most efficient, perform the best in most conditions, and last the longest.They cost more, but are worth it. The first single crystal solar cells made by Bell labs in the 1950s still produce electricity!
	Multi Crystal: (polycrystalline) Each cell is made of many crystals. They work well and are cheaper.
	Amorphous: these cells are grown without crystals at all. They are good for specialty applications like roofing or RVs, because they can work if shaded, and can bend. They can deteoriate in sunlight and are the least efficient.

Cell Structure	Brand Samples	Performance in the below conditions			Warranties
		Early Morning & Late Afternoon	Part Shaded	Hot Weather
Single Crystal	Solar World SunModule	Best	Poor	Best	25 years to 90%
Muti Crystal	BP Photowatt Kyocera	Ok	Poor	Ok	20 years to 90%
Amorphous	Unisolar	Good	Ok	Good	20 year to 80%

Solar Panels convert the energy from the sun into DC Electric Current which is either stored in Solar Storage Batteries, used directly to run DC items such as Well Pumps or other DC Appliances, or it is Inverted into AC Current and sold back to your local utility.

We offer Solar Panels from a number of different manufactures and in a variety of sizes to meet your solar projects needs. Below you will find a listing by brand names.

PV modules are rated at Standard Test Conditions (STC). These are almost perfect conditions in which full sun is shinning straight on the module and the module temperature is 77 deg F.  These conditions actually occur in the winter for a few hours on clear days, but are not a complete picture of the module's performance year round in a real life situation. 

Another standard is being used (PTC) which measures air temperature (usually a module is much hotter than the surrounding air). Modules are usually derated from 10% to 25% under this rating system.
 

Module Rating	Description
Maximum Power Pmax	The most watts produced by a module under standard test conditions. In Real life conditions a module may make only 80 to 90% of this rating, due to heat, dirt, wire losses, and the fact that the module may be operating at lower voltage.
Voltage(max power) Vmp	The voltage at which a module makes its most power. (For example, a 12 volt nominal module, Vmp can be as high as 17 volts.)
Voltage (open circuit) Voc	The module's highest voltage at no current. (A 12 volt nominal module may go over 22volts)
Amps (max power) Amp	The current at the module's Max Power Point. (usually around 90% of short circuit current)
Amps (short circuit) Asc	The highest current the module can make at no voltage.
Maximum series Fuse	The largest amp fuse or breaker to use with the module.  (modules with a higher rating, can be paralleled in some cases to save on wiring and breakers)

Its easiest to compare modules on a dollars per watt basis. (Divide the module's OUR PRICE by its power rating) Just because one module is cheaper than another means nothing without comparing the OUR PRICE per watt. Also mono crystalline is worth 10% more per watt, because it will make more power throughout the day and throughout the year than the same wattage module in polycrystalline.

Wiring Modules

Solar modules are wired in different combinations to get the voltage & current needed. They are wired in series to increase voltage; up to 30 modules can be strung together for voltages as high as 600 v (the highest voltage most modules are rated for). The voltages of each module are added together. (see Wiring Diagrams for series and parallel wiring)

Modules are also paralleled to increase current. The voltage stays the same, but their currents are added. Some 12 volt systems can have dozens of modules in parallel for currents close to 100 amps. To avoid too much current in a single module that can overheat and melt connectors, the modules are wired into subarrays. Each subarray carries as much current as the modules are designed for including a safety factor. This factor includes both a 25% safety factor and a 25% factor in case the modules produce more than their rated power in special sunlight conditions (see edge of cloud effect in glossary).

Example:
If a module's series fuse rating is 20 amps, then you divide that by the combined safety factor of 1.56. so you could safely wire 12.8 amps of modules together in parallel. If each module's short circuit current is 4.2 amps, then you could parallel 3 modules. Regardless, we don't recommend ever wiring more than 4 modules in parallel in one sub-array, and some inspectors don't allow any parallel wiring within a sub-array.