How to connect solar inverter to grid?
Solar electric systems can be divided into two categories:
- Off-grid (not connected to the power grid and uses batteries to store generated energy)
- On-grid or grid-tied (connected to the power grid where excess energy is transferred)
In this article, we will describe how can grid-tied systems be connected to the grid.
The 120% rule
When it comes to designing a solar PV system for any residential property, the 120% rule is used to determine the limit of how much new power generation the site’s electrical infrastructure can safely handle.
This rule is based on Main Breaker and Bus Bar ratings.
The calculation to determine the limit is maximum electrical equipment load which is Main Breaker Rating x 120%
An image of a regular domestic distribution panel
How big of a solar breaker can I install at my house?
If your service is 200 A:
200 A x 120% = 240 A – maximum load
This means that the solar breaker is limited to 40 A because the Main Breaker Rating + Solar Breaker must be less than or equal to 240 A.
200 A + 40 A = 240A
200 A + 30 A < 240 A
The Main breaker is usually installed at the main electricity line going into your home.
If your service is 100 A:
100 A x 120% = 120 A – maximum load
This means that the solar breaker is limited to 20 A because the Main Breaker Rating + Solar Breaker must be less than or equal to 120 A.
100 A + 20 A = 120A
100 A + 10 A < 120 A
The Bus bar is the part of the distribution panel where you install breakers.
What if I want to install a bigger system?
If your system amperage exceeds the 120% rule, don’t worry! You can still tie your system to the grid using piercing lugs (or inline lugs). They are used to manually connect PV supply wires with electricity supply wires.