Photovoltaic Solar Systems
Photovoltaic panels, also known as PV panels, are designed to absorb sunlight and convert it into useable electricity. A homeowner who is converting to solar power has options to tie into the local electricity grid and either sell the excess electricity back to the power company, or store the excess energy produced by the PV panels in a battery for situations where the power company has a blackout. Grid-tie systems can save a homeowner a lot of money, as the electric company will either buy the extra power produced or credit the homeowner's account for power usage in the future.

• "Grid-Tied" PV systems use special inverters that allow electricity to flow safely back into the electric grid, augmenting the utility company’s electric capacity. Grid-tied PV systems may have battery back-up capability (with additional cost), but are not necessary to the system. Grid-tied PV systems are an extremely effective way to generate your own "clean" renewable energy from the roof of your home.
  
  
• "Off-Grid" (or stand-alone systems) are exactly that. They are completely independent of a utility company and almost always use some kind of electric back-up system for surge power and night time electricity needs.