The ability to harness the sun's free energy is not new to the 21st century, I'm sure at some point in your life you've handled a solar calculator that didn't need batteries and stayed on as long as there was light. That same technology but on a larger scale is what getting a Photovoltaic system for your home is like. A system can be designed to eliminate your entire electric bill or you can choose a smaller system that eliminates the top tiers (most expensive parts) of your electric bill.
Solar Modules are usually installed on rooftops where they get the most sun exposure or on a custom rack should good space be available. Each solar module has numerous photovoltaic cells traditionally made of monocrystalline or polycrystalline silicon. When struck by light, the cells absorb a portion of that energy converting it to DC power. Since we use AC power in our homes, the electricity produced by the cells is sent through an inverter converting the energy to AC power for use in our home.
Virtually all of the Photovoltaic systems installed in California are "grid tied" systems, meaning the systems are installed to directly connect to your power supplier. During daylight hours any surplus electricity generated by your solar electric system is fed back into the PG&E grid and your PG&E account is credited for the excess electricity you produce. When the sun goes down and your solar electric system is no longer able to generate power, the excess electricity you produced during the day is used to credit your PG&E account for the power you use at night. With a properly designed and installed solar electric system you can eliminate your electric bill.