Rooftop Solar is Also Off in a Power Outage

Rooftop Solar is Also Off in a Power Outage

Brian Wang |
October 9, 2019 |

PG&E is shutting off power to 800,000 Californians today and tomorrow. More than 1 million California homes are already soaking up sunshine with solar panels to generate electricity. Next year, that number will surge as new building standards take effect requiring all new homes permitted after Jan. 1 to have solar photovoltaic systems.

More than 868,000 California homes have solar panels that are interconnected to the state’s power grid, with a total generating capacity of almost 4.8 million kilowatts. Those solar panels connected to the grid will also be shut off if they are in areas where PG&E is cutting off power. Those homes will only have power if they have battery backup like the Tesla Powerwall or a gas generator.

California has 10-11 million homes.

Why Solar is Out in a Power Outage

There are two reasons that ordinary grid-tied solar will not work during a grid failure. There is a technical reason and also for safety and regulations.

The electronics that control a solar energy system constantly adjust voltage and current to keep the panels operating efficiently as the sunlight changes. The system produces quantities of power that are not dependent on how much your house is actually using in a given moment. In a grid-connected system, any excess power is put back onto the grid for others to use, and your utility credits you on your bill for that power.

During a power outage, the power utility sends out repair crews to find and fix the points of failure. Linemen and women will be jeopardized if there is a local power generator (like a solar array) leaking power onto the grid lines. Solar arrays must automatically shut down per utility regulations.

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New inverters with a secure power supply (SPS) feature allow connection to an external socket outlet. They provide up to 1,500W of daytime power when the sun is shining and the array is generating sufficient power in the event of a grid outage.

A battery backup is usually needed to provide power in an outage. This can increase costs by many thousands of dollars.

SOURCES- Tesla, CALSSA, Third Sun Solar

Written By Brian Wang,

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