Often, when I am about to charge an electronic device that I bought in one country in a different
country, I look at the label which lists the voltage and frequency for which the adapter is
designed. Most adapters are usually marked 100-240V, 50/60Hz, which covers everywhere around the
world. So, the only thing that is required is a physical plug converter. But sometimes, you might
run into devices that are marked 220-240V, 50 Hz (AC supply in India) or 100-110V, 50/60Hz (AC
supply in Japan) With such single voltage only devices, one must use a step-up or step-down
transformer when using the appliance in a country with a different supply voltage. (There is no
converter for frequency itself and appliances with motors will probably suffer when the frequency
changes.)
One of the questions I started thinking about recently was whether one might be able to put some Solar panels outside, connect it to a battery, and run a small generation system at home which would supply power directly at 110 V (or 220 V if you are in the opposite situation). Is that a viable option? Solar panels are becoming more and more prevalent in both India and Japan and I am seeing a lot of individual houses that are making the capital investment, which is supposed to be recovered in 18-36 months.