This sort of solar charger is great for emergencies and when you're on the move. But, frankly, the amount of energy (or money) they save is pretty negligible, especially when compared with your total household consumption.
The total energy consumption to charge an e-reader, MP3, phone and camera over the course of a year is typically less than a few minutes of running a central heating and hot water system. And evern less that a single short journey by car.
By all means, use a solar charger if you want to cut your energy use to an absolute minimum. But, first, turn your thermostat down by half a degree (or put on a sweater next time you're feeling chilly). Or use a bike or your feet instead of a car for one short journey per year.
Mike
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