Most people who get home solar panels do so to save money, but greater energy independence is a big draw, too. However, most grid-tied solar panels shut down during a power outage, so do you really gain any independence? Yes, you can, with the right help and planning.
The right battery set up can keep your lights on during an outage and keep your panels from a potentially dangerous condition called solar islanding. Here’s what you need to know.
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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. However, your grid-tied solar power system still produces electricity.
- Once the panels have supplied electricity to your home, any excess energy goes into the grid.
- Meanwhile, utility workers are repairing power lines they think have no power running through them. These workers might come into contact with live wires.
- Any contact with a live wire can lead to severe injury or death.
Islanding, in the general energy industry, is also a term for intentionally sectioning or islanding the power grid to limit the possibility of a cascading blackout. If one island has an outage, it’s less likely to spread to more of the grid.
Luckily, if you 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 Solar
The vast majority of homes with solar panels remain tied to the grid, which means you have access to electricity from the grid if your home is using more than your panels are creating. If the grid goes down, your solar system is designed to turn off automatically to ensure the safety of utility workers fixing 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.
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 their inverter is fitted with anti-islanding protection, it simply means it has islanding detection (often based on voltage and frequency detection) and detects when the grid is down. That way, it stops feeding power back to the grid and protects 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
Islanding in solar panel systems leads to grave safety concerns to utility workers working on a grid they think is “dead.” Solar anti-islanding ensures these workers are safe from burns, shock, and death.
2. Solar anti-islanding keeps the grid equipment safe
Grid infrastructure is built to 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 overload and damage to inverters, rendering them non-functional.
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 solar panel 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.
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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.
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.
- Scenario 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.
A Battery Can Keep Your House Powered During an Outage
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 reliable batteries with sufficient capacity.
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 your grid-tied system is capable of creating an energy island, 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.
Going Solar at Home
Anti-islanding protects your solar panel system, the larger electric grid, and other people from danger and damage. However, your home can be a solar energy island with renewable energy available during a power outage or blackout. Integrating a solar inverter with island mode and battery storage will give you this capability while maintaining a connection to the grid.
If you want a solar power system that can safely provide energy during a power outage, plus give you energy bill savings and meet your family’s needs, working with an experienced, professional company is the best way to design the system you need.
Palmetto’s experts can review your situation, provide recommendations, and answer your questions. You can get started today with our free solar savings calculator or by contacting us.
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Frequently Asked Questions
What is islanding, when it comes to electricity and solar panels?
Islanding, with home solar power systems, refers to a system generating electricity during an outage. Sending power to the grid during a power outage is prohibited.
Why is islanding a problem for the grid?
Solar islanding creates major safety hazards and possible damage. It can cause costly damage to the power grid. It is also a hazard which can cause injury or death to utility workers.
Will solar panels work during a power outage?
Solar panels can generate electricity during a power outage. If your solar panel system cannot separate from the grid, it will shut down by design when the grid is down. If you have battery storage and specialized inverters as part of your solar power system, your battery can power critical loads and your solar panels can keep generating power.
Disclaimer: This content is for educational purposes only. Palmetto does not provide tax, legal, or accounting advice. Please consult your own tax, legal, and accounting advisors.
Andrew GiermakWriter and EditorAndrew joined Palmetto in Charlotte in August 2024. He’s been a writer in journalism, then in business, going back to almost the 20th century. He’s lived in Indiana, Virginia, Pennsylvania, Virginia again, and now North Carolina for the last 12 years. He likes golf. Is he good at it? Not so much.
