The term “grid tied” refers to energy systems that interface with the existing utility grid.  These systems are the simplest to install and most cost effective to buy.  They make the most financial sense when utility rebates and tax credits are applied.  Many times these incentives can cover over 70% of the system cost.  Grid tied systems work by producing clean power from the sun, wind, or water and selling any excess electricity that is not consumed back to the utility.  At night or at times of insufficient wind you are purchasing power from the utility grid as normal.  If your system produces as much electricity as you use during an average year, you have successfully eliminated your electric bill.  With net metering laws any excess power generated must be paid to the customer by the utility, and this comes in the form of a check at the end of the year. Because these types of systems do not rely on any battery storage maintenance, total system costs are greatly reduced.