How On-Grid or Grid-Tied Solar Energy Systems Work
What’s the difference between GRID TIE and OFF GRID solar systems?
Grid Tie means that your solar system is hooked into the utility company. Off the grid means you are not connected to the utility company.
It’s more efficient to be hooked to the utility grid because off grid systems must store the energy, as in batteries. If you are on the grid, the utility company stores the energy. The utility company keeps track of the kilowatts you use on an hourly basis. During a sunny day, you can produce more energy than you are using so your electric meter goes backwards and you build up energy credits. The goal of your solar power system on the grid is to produce as much power over a twelve month period as you use.
ON THE GRID DURING A SUNNY DAY
Solar electric systems generate electricity silently and without any moving parts. Sunlight falls on the solar array and generates DC electricity. That DC electricity is converted into household 230V AC electricity by the inverter. The AC electricity is fed into your electric meter and circuit breaker panel. The electricity either goes to your appliances and lights, or to the grid, or some to each. This happens silently and automatically every day.
ON THE GRID AT NIGHT OR DURING A CLOUDY DAY
At night and during cloudy weather, the solar system’s output is reduced or stopped; however, your home then gets electricity from the utility grid. You are always connected to the grid, so you can have as much power as you need, any time you need it, regardless of whether the solar system is able to put out any power.
When the solar system does put out power, it reduces your usage at the time, or, if there is excess, your meter spins backwards, counting down your electric use and bill. Special metering, such as Time-of-Use metering and billing arrangements can help you take advantage of higher daytime rates, allowing you to sell power at a high rate and buy it back at night at a lower rate. This helps reduce the necessary size of your solar system while still cutting your bill by the same amount. The only catch is that during a utility power outage a standard grid tie system will not produce power until the grid power is available. If this is a issue read on.
GRID TIE WITH BATTERY BACKUP refers to a system that has all the advantages of both a grid tie system and an off grid system. When utility grid power is available the system works just like a standard grid tie system and sells excess power back to the utility. But unlike a standard grid tie system, when the utility power fails the battery backup allows the solar array to continue to supply the home with power during the day, and the batteries can supply select circuits within the home during the night. Once the utility grid starts up again the system automatically switches back to normal operation.
How much will solar power save on your electric bill?
How much you can save depends on your usage and variations in weather. However, say your monthly electric bill is $132 a month when averaged over a year. With solar power your bill could average only $8 a month. The reason we can't reduce it to zero is that most utility companies will charge a minimum payment for connection to the grid. There is no sense in having a larger solar array that would bring your overall usage to zero.