The PV Panel
The solar photovoltaic (PV) panel produces a current when light strikes the panel. The more light that strikes the panel the more current it produces. The panel is rated by its ability to produce current in direct sunlight in the form of power. The common unit for power is the watt. A 50 watt panel will produce 50 watts of power in direct sunlight. If this panel is in direct sunlight for one hour it will produce 50 watt-hours of energy. Energy is the important quantity in sizing your solar system.

Energy
A good analogy for understanding energy is to think of it like water, and think of your solar system as a rainwater collection system. You collect a certain amount of water each day, store it in a tank and use a certain amount each day. Energy is similar: Your system collects a certain amount each day via the PV panel, stores it in a battery, and each day some is used to power your load (lights, TV, etc.) When your system is empty it must collect more energy before it can power your load, when your storage (battery) is full it cannot accept any more energy until some is used. The common unit for energy is the watt-hour or kilowatt-hour (1000 watt-hours). Your power company charges you for each kilowatt-hour you use.

Power
Power is the rate at which energy is used, for example: watt-hours per hour (or simply, watts). An appliance with a rating of 1000 watts will use up energy 10 times as fast as one with a 100 watt rating. So it is very important to know how much power your load uses and how long it runs for each day.

AC vs. DC
AC stands for alternating current and is what you get out of an outlet in your house. DC stands for direct current and is what your car battery (and solar batteries) provides. A solar system needs a DC to AC inverter to provide the same kind of power found in your home. So if you plan on running a “normal” appliance you need the inverter in your system, if you only plan on using 12 volt DC loads you do not.

PowerPod size examples:
A typical small system for rural applications would include a 50 watt PV panel and a 100 amp-hour battery (about 1200 watt-hours of energy storage). It will run:
... a small DC 100 watt TV for 2 hours after a sunny day
or ... a 50 watt radio for 5 hours after a sunny day
or ... 3 10 watt lights for 9 hours after a sunny day
or ... some combination of the above.

A fully loaded small PowerPod system would include a 100 watt PV panel and two 100 amp-hour battery (about 2400 watt-hours of energy storage) and an inverter for AC loads. This size works well for a large solar home system, remote cabin power or even a portable generator for short duration power use. It will run:
... a small DC 100 watt TV for 5 hours after a sunny day
or ... a coffee pot long enough to make good coffee, some lights
to read by, and a radio/tape player for listening to music and news.
or ... will collect about 0.5 kilowatt-hours on a sunny day.