Solar power and technological gadgets are two things that interest me, and I recently obtained a small, portable solar charger which allowed me to fulfill my dreams of charging my devices with free, universally available power. Well, almost. It turns out that while these devices may be tempting gadgets, they’re really of limited practical use.

In order to get a full charge, most small solar chargers need a full day of direct sunlight – which means you need to locate your charger next to a southern-facing window or somewhere outside. If it’s inside, you’re probably at home or somewhere where electricity is available, in which case I can pretty much guarantee you that if you’re using such a charger to save a little money, you’re probably talking about a few cents over the course of the year due to the small amounts of electricity these portable chargers provide – and that’s if both the weather and your patience allow you to get that much use out of it.

If you set the charger up outside then it needs to be somewhere you can keep an eye on it so that no one snags it (assuming there are people around who might) or in case it rains (unless it’s waterproof, in which case the charger may be safe, but you won’t get much of a charge).

If the device doesn’t have internal batteries which store the solar charge so you can use to transfer it to your phone or MP3 player later, then you’ll also have to leave your device connected to the solar charger the entire time. Again, consider the above.

If it does have internal batteries which allow you to transfer the charge, there’s an inherent flaw with this design: the greatest threat to the life of rechargeable batteries is heat – yet in order for this device to work best, it needs direct sunlight. I’m not saying such solar chargers won’t work, but if you buy one and intend to use it frequently, I suggest you get one that at least allows you to replace the rechargeable batteries yourself.

When it comes down to it, I see these devices as being handy in two situations:

1. Extended excursions in the wilderness for charging a GPS, phone or MP3 player. This is especially true for devices where replacing the battery with a second, charged one isn’t an option, such as with an iPod and some other MP3 players, or where other charging devices that rely on batteries will only get you one or two charges. If you’re really headed out into the middle of nowhere for a long period of time, this may even be an essential survival device if you’re dependent upon your GPS. Keep in mind that you’ll be hiking during the day, you may need to rig your solar panel to the top of your backpack in order to get a charge (and even that will be pointless if you’re hiking in a shady forest).

2. In case of extended power blackouts assuming no access to a car charger, a gas generator or other power source. In the case of an extended blackout, you could use a portable solar charger to keep your device topped-up on days when the sun allows a good charge.

Outside of the two situations above, I think you’d be better off with a device that can charge your phone or other device using standard AA batteries, such as the Energizer Energi To Go devices, or one that has a hand-crank and dynamo, such as this one which also features a radio and LED flashlight. Either of these or similar devices will allow you to give your phone an emergency charge regardless of whether the sun is out.

While for a select few people these portable solar chargers could be a life saver, if you’re really interested in getting into solar power, perhaps your money would be better spent on a good book on how to setup solar power for your home instead.