A grid tie solar system is a solar power installation that interacts directly with a power grid through a special type of inverter. Gird tie systems can operate without batteries and allow you to sell, or at least feed, any excess energy you produce back into the grid system where it can be used elsewhere.
Grid Tie Inverter
Inverters are used to convert direct current (DC) into alternating current (AC), which is required to power your household appliances. Grid tie inverters allow you to feed excess power back into the main power grid, causing your electric meter to spin backwards, earning you credit with the power company.
National law requires any investor-owned power company to allow grid tie systems. However, electronic cooperatives like those often found in rural areas are permitted to opt out.
Grid tie systems range in price according to the amount of electricity they produce. Low-output systems start at around 175 Watts and cost between $1,500 and $1,800, whereas high-output systems producing upwards of 2 kilowatts of power cost around $16,000. There are residential systems available that produce as much as 13 kilowatts.
Many states offer grants and tax breaks for residents who purchase grid tie solar systems. Your cost can also be reduced by selling more energy back to the company. However, many companies only offer reimbursement in the form of credit. There are also some federal incentives available.
One of the advantages of a grid tie system is that you do not need a battery bank. When your house is not being powered directly by your solar panels you simply pull energy from the grid. However, grid tie systems can be built with battery banks for backup.
Oasis Montana Inc.: Batteryless Grid-Tie Electric Power Systems
Mr Solar: MrSolar Brand Clean Energy Grid-Tied Home Solar Energy Systems
Go Green Solar: Grid Tie Solar Electric Systems
Database of State Incentives for Renewables and Efficiency