For rating the power of solar panels, the term "STC" is used: it stands for "standard test conditions". STC means 1,000 watts per square meter at 25°C, and represents an average sunlight. For warmer locations, the power output will often be less because of solar panel heating (typically panels run 20°C or 36°F over ambient temperature, at least). Efficiency is a measure of how much of the sunlight that hits the panel will be turned into electricity. It is calculated with the rails and empty spaces of the module in mind.
Four types of connecting methods are commonly used for photovoltaic modules: MC/MC3, MC4, Solarlok, and junction box. MC/MC3 and MC4 are single-conductor cables used to connect the module(s) to the inverter(s). They are designed so that there are only two connector polarities for both the sending and receiving end of the positive and negative leads. The sending positive is the same style as the receiving negative, and vice versa. In this way, the same extension cable can be used for both polarities, but is switched end-to-end to avoid accidentally reversing the polarity of the module. Junctions are also sold that enable the installer to put modules in parallel or series, depending on the requirements of the inverter. MC4 is the locking version of MC/MC3, required for some higher-power installations. More information can be found on the Installation Guide page. Solarlok is similar to MC4 but requires a latch locking clip to be lockable. A junction box is a small plastic enclosure mounted on the reverse side of the solar module that has screws with clips to attach to stripped wires.
The Single-Sided PV Modules page is quite extensive because of the large number of available modules. The table can be sorted by clicking on the header titles. Currently Sanyo is the only manufacturer producing double-sided modules (at least on a large scale); see the Double-Sided PV Modules page for their selection. Note that the watts listed there are for single-sided operation - Sanyo claims that up to 30% more power can be achieved by including reflectance from the ground. Double-sided modules would be used when an awning or similar structure is to be made, though they are not required. Visitors are encouraged to do independent research at Sanyo's web site about this new type of module.