Portable solar panels, although relatively expensive when compared to grid electricity, are especially useful for outdoor activities like camping and hiking, or for trickle charging your boat or RV. In case of a power cut they make a great backup. For portable panels normally 12 volt solar panels are used.
If you are planning to buy portable solar panels you have to take into account some extra expenses. These are additional connection equipment in order to use your panels. See to it that the connectors fit with the recharging plugs on the devices you want to use. Buy a set of battery clips if you plan to "trickle charge" your vehicle or boat.
To "trickle charge" your car, place the portable solar panel in a sunny spot, then plug it into the cigarette lighter socket, or attach the clips to the vehicle's battery. This will keep the battery fully charged.
Since portable solar panels are reduced in size they do not generate the same amount of energy output as their larger cousins. They will not heat your entire house, but they will recharge the batteries of your cellphone, iPod, GPS and such devices. In the same way as large solar panels they operate by generating energy from sunlight. Therefore it's important to place them on an open surface under direct sunlight.
An important tip: make sure that the portable solar panels you buy have a built-in regulator. Without a regulator you run the risk of frying any device by overcharging its battery. The regulator will automatically adapt the energy output to the required amount.
Portable solar panels, by the way, are not all that difficult to make, and you can save some energy costs. If you're into hobbying visit my website http://solarpanelresidential.net for a good DIY manual.