Grid Tied Solar System

A grid tied solar system has a number of aliases such as grid-connected solar system, grid-intertied solar electric systems, on-grid solar system and grid-tied photovoltaic systems. I’m sure there are other aliases but they are the most common.

A grid tied solar system is one in which your solar power system is connected to the power grid. This enables you to sell any excess power you produce back to the electric company through a plan known as net metering.

Net metering is an electricity policy for consumers who own renewable energy facilities, such as wind, solar power or home fuel cells. Once a consumer has signed up to a net metering program they will have a smart meter installed known as a Time of Use meter which actually runs backwards when you are selling electricity back to the grid.

Time of Use meters allow utility rates and charges to be assessed based on when the electricity was produced. Typically the cost of electricity is highest during the daytime peak usage period and low during the night, when usage is low. This is good news for owner of grid tied solar system as solar power systems produce all their electricity during the day.

Most States have their own net metering policy with slight variation between states such as the maximum size of the grid tied solar system and the tariff that is payed to the consumer. The maximum size specified for a grid tied solar system typically range from 10Kw to 2Mw in Colorado.

Sources that produce direct current, such as solar panels must be coupled with an electrical inverter to convert the output to alternating current, for use with conventional appliances. The phase of the outgoing power must be synchronized with the grid, and a mechanism must be included to disconnect the feed in the event of grid failure. This is essential if workers repairing downed power lines must be protected from "downstream" sources, in addition to being disconnected from the main "upstream" distribution grid.

Off Grid Solar System

The alternative to having a grid tied solar system is an off grid solar system, also known as independent or stand alone power, these systems are typically used to power remote homes and cabins. In most cases, if the power lines are more than 1/3 of a mile away, a stand alone renewable energy system can be cost-effective.

During day light hours when the sun is shining, solar panels are used to charge a bank of batteries and also supply power to the home. As the sun goes down and the solar panels stop producing electricity an inverter converts the stored DC battery current to standard 120/ 240 volt AC power. This power is then fed to the properties electric system supply electricity to lights and appliances. These systems can easily accept other battery charging sources such as wind turbines, hydro electric turbines and AC generators. When 2 or more charging sources are used, it's known as a hybrid power system.

The disadvantage with an off grid solar system compared with a grid tied solar system is that you don’t have a power source backup (you’re not connected to the power gird). If you have dark winter’s day and your batteries are not fully charged then it’s possible that you might run out of power before the sun rises. If this is going to cause a major headache for you then a backup generator could be an option.