Electric Knowledge Needed Please

[buckeyefarmer]

I am getting to know my grid-tied solar electric system and have a question.

The inverter sends its output to the buss bars of the service panel through a backfeed breaker, the utility power is applied to the buss bars in the same panel.

My question is, what determines when/if power from the inverter is used versus power from the utility? I don't know the electric theory behind this and I wish I understood it a little bit at least.

Thanks.

Google Kirchhoffs current law.

Your bus is a node. It has incoming power from the solar, incoming or outgoing power from the utility, and outgoing power to all your house breaker loads. If your house load is greater than your solar source, then you will use your solar power and draw additional from the utility. If your house load is less than your solar source, they you will transmit power out to the utility to other loads.

 

[dave1949]

Google Kirchhoffs current law.

Your bus is a node. It has incoming power from the solar, incoming or outgoing power from the utility, and outgoing power to all your house breaker loads. If your house load is greater than your solar source, then you will use your solar power and draw additional from the utility. If your house load is less than your solar source, they you will transmit power out to the utility to other loads.

Thanks for your explanation! I can see that much more clearly after looking up Kirchhoff's law, found some tutorial info. I like to have at least a fuzzy idea of what happens and why.

 

[Alien]

There are inverters that allow you to use your solar if the grid goes off and you do not need a massive battery bank like an off grid system. For example Selectronic - On-Grid Inverters with Battery Backup
Also SMA make a similar one.

 

[dave1949]

There are inverters that allow you to use your solar if the grid goes off and you do not need a massive battery bank like an off grid system. For example Selectronic - On-Grid Inverters with Battery Backup
Also SMA make a similar one.

That's good to know.