Grid-tied systems have safe interconnection with a utility grid. Under net-metering (or net-billing) grid-tied systems allow to:
- consume on site the generated solar power when it is available and the utility grid is working;
- import electricity from the grid when site consumption exceeds solar generation;
- export excess of solar power to the grid and receive a credit for exporting power.
Grid-tied systems under net-metering regulations are the easiest way to produce and consume solar electricity generated at the site. A bi-directional meter records cumulative energy sold to the grid and purchased from the grid. The utility bi-directional meter only defines the cumulative energy that passes through the meter, however it does not record total generation or total power consumption at the site. In order to have a full picture about generation and consumption, we recommend installing separate energy meters.
Larger scale solar systems and solar farms connect to the distribution grid though a revenue meter. Unlike bi-directional meters, revenue meters record total solar generation in the absence of the electric load.
Simple grid-tied systems do not provide outage protection. When the utility grid falls, these systems must turn off for safety reasons.
Grid-tied systems with Secure Power Supply (SMA term) are developed to provide up to 20amps of solar generation during utility power outages. When the grid fails, a system owner turns the switch on to enable the Secure Power Supply. An inverter isolates the solar system from the grid and generates up to 20 amps of energy for as long as it is sunny.
Adding a battery back-up to the system and re-wring loads to a critical panel adds to the costs, but ensures your lights are on during the grid outage. Batteries can be integrated to the system by one of the following three methods:
- Installing a hybrid inverter ( e.g. Tesla PowerWall2; SolarEdge StorEdge, Fronius Symo Hybrid, etc).
- Building AC-Coupled system by adding battery-based inverters (e.g. Magnum MS4448PAE, SMA Sunny Island, Outback Radian) to the existing grid-tie inverter.
- Bulding DC-Coupled system using charge controllers and battery-based hybrid inverters (e.g. Outback Radian)