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Solar Islanding and Anti-Islanding: What You Need to Know

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An island, representing a solar-powered home that's generating its own power separate from the grid, also known as solar islanding.
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One of the main reasons people invest in solar power is to gain energy independence from the utility grid. However, adding a solar panel system doesn't necessarily mean that your home is immune to power outages or blackouts. During such an event, your grid-tied system might be turned off automatically to protect the grid from “solar islanding”. To keep generating power, you need to become your own solar energy island.

Understanding how your solar panel system works—especially when it comes to safety features—is important. In this guide, we'll explain everything you need to know about solar islanding, including its dangers, the importance of anti-islanding safety measures, and the relationship between effective solar islanding and battery storage.

What is Solar Islanding?

Solar islanding is when a home solar power system continues to generate electricity even though the grid is down. Many people would consider this a good thing, as your home still has power from your solar panels while everyone else has no power.

However, things become dangerous when your solar panel system produces electricity, and it goes into the grid. This situation poses serious safety concerns to utility workers who are trying to fix the grid, as they could be injured if the grid is still "live".

Here's what could happen if solar islanding wasn’t prevented:

  • The local grid goes down.
  • Your grid-tied home solar power system still produces electricity.
  • Once the panels have supplied electricity to your home, any excess energy flows back into the grid.
  • Meanwhile, utility workers are repairing damaged power lines on the "should-be-dead" grid.
  • With energy still in the grid, these workers might come into contact with a live wire.
  • Any contact with a live wire can be catastrophic, leading to severe burns, shocks, or even death.

Luckily, if you still want to use your solar power during a power outage, you can set up your home for safe islanding. We’ll explain how, in more depth, later in this article.

Grid-Tied Solar Vs. Off-the-Grid

The vast majority of homes with solar panels remain tied to the grid, which means you'll have access to electricity from the grid if your home is using more than your panels are creating. If the grid goes down for any reason, your solar panel system is designed to turn off automatically to ensure the safety of utility workers who might be fixing any damaged power lines.

On the other hand, if you're completely off the grid, you're already on your own power island. Your islanding solar inverter works independently from the power grid. If there's a storm or other event that knocks out the main power grid, your solar power system will continue running and providing power to your home.

We mention this because many people mistake going solar with going off-grid, but that's typically not the case. To be truly off-the-grid, you must generate 100% of your electricity without depending on the distribution system operated by the local utility company. As you'd imagine, that isn't easy to achieve because your home still needs electricity when the sun isn’t shining, so you typically need a large battery backup system to store extra electricity.

(To learn more about going off-the-grid, check out: What "Off The Grid" Means – Does Solar Mean Going Off-Grid?)

What is Solar Anti-Islanding?

Solar anti-islanding is a safety feature built into grid connected solar power systems that can shut them off and disconnect them from the grid during a power outage.

If you hear someone say that their inverter is fitted with anti-islanding protection, it simply means that it has islanding detection (often based on voltage and frequency detection) and can sense when the grid is down. That way, it can stop feeding power back to the grid and protect the utility workers.

An anti-islanding solar inverter might seem like a small detail, but it's important because:

1. Solar anti-islanding ensures the safety of workers fixing the grid during an outage

Like we mentioned earlier, islanding in photovoltaic (PV) systems can pose grave safety concerns to utility workers who might be fixing a "should-be-dead" grid. Solar anti-islanding ensures that these workers are safe from burns, shock, and even death.

2. Solar anti-islanding keeps the grid equipment safe

The grid infrastructure is set up in such a way that it will shut down when it detects a severe problem. Without solar anti-islanding protection, your solar panels will continue to send voltage back to the grid, which could damage the grid hardware and lead to other costly losses.

3. Solar anti-islanding prevents inverter damage

Solar islanding could cause damage to inverters, rendering them non-functional. Anti-islanding exists to protect your inverters from overload and save you from costly damages.

Is it possible to find a modern grid-tied solar system that lacks anti-islanding protection? The short answer is no. UL Standard 1741 requires every grid-tied PV system to have a built-in anti-islanding solar inverter, and the solar industry follows that standard. While these laws were initially meant to protect utility workers, they've since been amended to include protection for your solar panel system and electricity grid at large.

Role of the Inverter in a Grid-Tied System

A solar inverter performs one main job: converting the DC electricity from solar panels into useful AC power for your home. Think of it as the brain behind the workings of your solar energy system. (For a more thorough explanation of this process, check out Solar Inverters: Types, Benefits, Costs, and How They Work)

When your solar-powered home connects to the grid, the inverter acts as the middleman. Often called a grid-tie inverter, this device allows your home to have uninterrupted power, no matter the amount of energy your panels are producing.

Grid-tie inverters know when and when not to deliver power, and they will synchronize power delivery with the grid. This quick and constant process allows your home to have all the power it needs when it needs it, and it will remove your system from the grid when anti-islanding is needed.

Here are three scenarios that explain the role of a grid-tie inverter more clearly:

  • Scenario 1: When your solar panel system generates some energy, but not enough to power all your devices, the grid-tie inverter combines solar power with grid power.
  • Scenarios 2: When your panels generate more power than your home consumes, the inverter redirects that extra power into the main grid.
  • Scenario 3: When your PV system isn't producing electricity at night, the grid-tie inverter switches back to 100% grid power.

Grid-Tied Solar Islanding Requires Battery Storage

As we said earlier, your solar power system can be set up for safe islanding with a compatible solar inverter and substantial battery storage. With a safe solar island system, the inverter assumes a highly complex but crucial role during a power outage:

  • First, your inverter completely removes your home from the grid to fulfill anti-islanding requirements.
  • Your inverter then uses a transfer switch to connect your home directly with the solar power system in island mode.
  • Your home then draws clean energy from your backup solar battery storage system to supply power to any critical loads you might have.
  • From there, your panels can begin generating electricity again to power your home and refill your batteries.

By creating a small “solar energy island” your solar panels can keep operating your home without the risk of adding any unexpected electricity to the grid. To achieve this effect, you need special inverters that can operate in solar inverter island mode and big, reliable batteries.

Both the specialized inverters and backup battery storage required to power your home without the grid are more expensive than a typical solar power system. Then again, having sufficient backup battery storage ensures that your grid-tied system is capable of creating an energy island whenever you need it, so you never have to worry about power outages or other power issues. It's up to you to decide if your peace of mind is worth the extra investment.

Key Takeaways

Anti-islanding exists to protect your solar panel system and the electric grid at large from danger and damage. However, your home can be a solar energy island that continues to have clean, renewable energy available, even during a power outage or blackout. Integrating a solar inverter with island mode and battery storage will help make this dream a reality.

If you want a solar power system that can still provide energy during a power outage, it's best to work with an experienced company like Palmetto. As a leading solar company, Palmetto can help you achieve increased energy independence with renewable solar energy, and we believe solar battery storage can be an important part of that process.

Get started today with a Free Solar Quote. Our experts can review your situation and provide recommendations on the right equipment and battery storage options for your home’s needs.

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