1.  Photovoltaic Cells (PV) - The basic unit of the system, these components directly convert solar energy into electricity.  The peak solar output is approximately 1 kWh per meter².  Many of these units are particularly sensitive to temperature fluctuations; the efficiency of cells will typically decrease by 0.5% for every 1^oC increase in temperature.  Cells can be arranged in series or parallel.

2.  Charge Controllers  - These units connect the PV cells to the batteries.  These complex devices regulate the charge that is delivered to the batteries to ensure that the correct voltage is supplied.  A charge controller will also protect the batteries from over charging, which would damage the batteries and severely reduce their capacity.  These controllers have a variety of options and technological improvements.  Most charge controllers use Pulse-width Modulation (PWM), an advancement that ensures the most efficient battery charging possible.  Some incorporate Maximum Power Point Tracking (MPPT), an advancement that maximizes the amount of current that is transferred between the solar array and the batteries by varying the voltage.  Others offer a Low Voltage Disconnect (LVD) option that will disconnect the loads when the voltage drops too far, thereby preventing possible system wide damage. 

3.  Batteries - Batteries store the DC electricity that has been gathered by the solar array.  Lead acid batteries are the most common variety used in these applications.  There are two types of lead acid batteries: Shallow and deep   cycle.  Shallow cycle (i.e. car batteries) are designed to provide large amounts of power over a short length of time, they are not discharged "deeply" and doing so will severely damage them.  Deep cycle batteries are designed to be completely charged and discharged "deeply" thousands of times.  These batteries must be completely recharged every cycle to ensure a long life.  If they are incompletely charged, the positive electrode plates will become sulfated and portions of the plate will be rendered useless.  Among deep cycle batteries, there are a few different options.  Sealed deep cycle batteries are often the ideal choice for solar systems because they are maintenance free.  Sealed gel cell batteries are another ideal medium, but these units are extremely sensitive to overcharging and will become inoperable.  Wet cell lead acid batteries are often ill-suited to solar applications because they require frequent watering and equalization to operate at optimal efficiency.  When choosing a battery, be sure to account for the longest expected "no-sun" period and increase this capacity by 20%.

4.  Inverters - Inverters will convert the DC electricity stored in the battery to the standard 120/240 VAC at 60 Hz, the same as the power supplied by a utility company.  These highly specialized devices will process the electricity, it will step, filter and transform the DC power into AC.  The more processed and "clean" the electricity is, the cleaner and quieter everything will run.  Conversion efficiency is negatively affected by the amount of processing that is performed on the electricity.  There are two types of inverters used in solar and alternative energy systems, Sine Wave (SW) and Modified Sine Wave (MSW).  Most appliances can use MSW electricity, this method is highly efficient.  There are some appliances that can be damaged by MSW, laser printers and some other devices using triacs need SW electricity.  Another drawback to MSW is that motors (including those in refrigerators) and power supplies run warmer and louder.  Some fans, audio system amplifiers and certain light systems can also have a resident "buzzing" sound.  Since MSW is ideal for 90% of appliances, it cannot be discounted as an option.  SW inverters provide the same electricity as the power companies and often exceeds the quality that they can provide.