While solar power is a wonderful, renewable source of electricity, it is not perfect; nor is it practical for all purposes.
It requires a fairly large number of solar panels to generate a sufficient amount of electricity for most homes. The classic rooftop panels may not be sufficient to your needs. This is why it is not uncommon for homeowners to need to buy electricity, even as they sell the electricity generated at the times they are not using any power.
Solar power generation is most effective in areas with a lot of sunlight. Places that get a lot of snow may find solar power systems only minimally useful in winter, even if they work well during the summer.
Theoretically, there is enough power in the sunlight that reaches the Earth's surface to out-generate all other sources of electricity currently operating. Practically, of course, solar energy is somewhat challenging to collect. The number of solar panels required to collect enough energy would cover a tremendous expanse of land.
Solar power is still somewhat more expensive to generate than more traditional forms of electricity, but since you are paying only for the costs of your system and its installation, you are still likely to save money over time. However, the initial investment is not small.
All in all, solar power has very few disadvantages. It is certainly not perfectly suited to all areas, but in many situations it is an excellent supplement to the electricity you purchase from the power company.