There a 4 big applications for photovoltaic solar cells:

1) In space

2) At isolated places

3) In apparatus with a low consumtion

Some pocket calculators or wristwatches work on solar energy. In that way, one does not need to replace the battery so often. Or sometimes, a battery is not even needed! If the solar cells receive enough light, electricity is produced for e.g. the calculator. This is possible because a calculator does not need a lot of electricity. In apparatus with a low electricity consumption, solar energy can be very advantageous, and profitable (new batteries cost money!).

4) In regions with a dense electricity network