If you are watching television and the power from the mains go off, then you can rely on an inverter. Likewise, if you are doing some important work over the computer and there is a power-cut, it is the inverter which can ensure continuity of your work.
Inverters come in various sizes. Their capacity is also different and so they should be bought in accordance to the use into which they will be subjected. Usually, if you are intending to feed power to larger appliances, then it is ideal to opt for a power inverter of a higher capacity. Most factories and firms opt for the ones which are colossal in size.
Power inverters can also be portable especially the ones which are smaller in size. People also carry them along with them to caravans and picnics. Thus, they can be of vital help at a place where you will not get direct electricity. At home, they serve as a backup and enable safe running of your refrigerator, air conditioner and other appliances.