If you have a rooftop solar power plant and there is a grid outage (a power cut), will the solar power plant continue supplying power to your load?

The immediate response from a prospective rooftop solar owner is: “Yes, of course. Isn’t that the whole point of having a rooftop solar power plant?”

But the answer is a bit more complex, and interestingly, it is not always a Yes.

To understand this better, let us consider the following scenarios of a grid connected rooftop solar power plant:

  • Scenario 1 – Solar + Batteries – Your rooftop solar power plant has battery storage but there is no diesel generator.
  • Scenario 2 – Solar + Diesel Genset – Your rooftop solar power plant does not have battery storage but is synchronized with a backup diesel generator.
  • Scenario 3Just Rooftop Solar – Your rooftop solar power plant has no battery storage, nor is there any diesel generator backup.

Let us see what happens under each of the above scenarios when there is a power cut.

 

For scenarios 1 & 2, as soon as the grid stops supplying power, the loads can start drawing the power they need from the batteries (Scenario 1) or from the diesel generator (Scenario 2). Thus, your loads and equipment can continue operating.

What about Scenario 3, the scenario in which there’s no backup from battery or diesel generator?

If there is no steady source of power available from your batteries or from your diesel generator, and if there is no power from the grid, can the solar power plant still continue supplying power to the loads?

The answer is: No. For Scenario 3, during a power cut, the solar power plant simply shuts down and does not generate power.

Why?

This is owing to two reasons:

  • Without a backup, solar power cannot reliably power your devices – imagine what happens to your TV and lights and fans if the sun suddenly disappears behind a cloud for 5 minutes!
  • A solar power plant cannot generate power unless there is a reference voltage, something that is usually provided by the grid power, or can also be provided by either the battery or the diesel generator. If the reference voltage is unavailable (which is the case in Scenario 3), the solar power plant cannot generate power.

In summary, a rooftop solar power plant can generate power during a power cut only if a backup option is available.

Stuff to Remember

Rooftop solar power plants can continue to generate power during power cuts only if there is a backup power source – such as batteries or diesel generator – available.