This is one of the most common questions Fresno homeowners ask when they start looking into solar. If the power goes out, will my solar panels still work? Most people assume the answer is yes. You have solar panels on your roof, they produce electricity, so it should keep your home powered during an outage. But the reality is a little different.
In most cases, standard solar systems do not work during a power outage. Whether your residential solar systemworks or not comes down to how it is designed and whether it has the right equipment to safely operate when the grid is down.
Why Most Solar Systems Shut Off During an Outage
To understand this, you first have to understand how most solar systems are connected. A typical solar system is what we call grid tied. That means your solar system is connected directly to the utility grid. When everything is operating normally, your system produces power, your home uses that power, and any extra power flows back to the grid. But when the grid goes down, everything changes.
For safety reasons, solar systems are required to shut off when the grid loses power. This is called anti islanding protection. The reason for this is simple. If your system continued to produce electricity while the grid was down, it could send power back onto utility lines. That could put utility workers at risk while they are trying to restore service. So, when your inverter detects that the grid frequency is no longer active, it immediately shuts the system down. Even if the sun is shining and your panels are producing energy, your system will not operate. That is why most solar only systems do not provide power during an outage.
The Role of the Inverter
The inverter is what controls whether your system can operate. In a grid tied system, the inverter needs to see an active grid signal in order to function. If that signal disappears, the inverter shuts off. It is not a limitation of the panels. It is a safety requirement built into the system. So, if your system is solar only, meaning panels and an inverter with no additional backup equipment, it will not power your home during an outage.
What Changes That: The MID Device
This is where things start to shift. If you want your solar system to work during a power outage, you need the ability to disconnect from the grid safely. That is where an MID comes into play. MID stands for Microgrid Interconnection Device. You can think of it as an intelligent, high speed transfer switch. Its job is to isolate your home from the grid when the grid goes down. When that happens, your home becomes its own microgrid. Once your system is isolated, it can continue to operate without sending power back to the utility lines. That allows your solar system and battery to keep running safely.
How a Solar and Battery System Works During an Outage
When your system includes an MID device along with a battery, everything changes. Here is what happens during a power outage. The MID detects that the grid has gone down. It immediately disconnects your home from the utility. At that point, your system is no longer tied to the grid. Your solar system and battery now operate independently. During the day, your solar panels continue producing electricity. That power first goes to your home, then charges your battery. At night, your battery discharges, and powers your home. All of this happens without any connection to the grid. Your system is essentially running as a standalone power source.
Examples of Systems That Include MID Devices
In today’s market, most full backup battery systems include an MID device built into them. It may not always be called an MID by name, but the functionality is the same.
Some common examples include:
- Tesla Gateway
- Enphase System Controller
- Franklin Home Power System Controller
- EG4 or similar hybrid inverter systems
These systems are designed to automatically isolate your home and allow your solar and battery to continue operating during an outage. If your system includes one of these types of controllers or gateways, there is a strong chance it has this capability.
Not All Battery Systems Provide Backup
This is an important distinction. Just because a system has a battery does not mean it will work during a power outage. There are battery systems that are designed only for self-consumption. These systems store energy to help reduce electricity costs, but they remain grid connected at all times. If the grid goes down, these systems will shut off just like a solar only system. They do not have the ability to isolate from the grid. These are typically used in areas where outages are rare, and the focus is purely on savings. So, if backup power is important to you, it is critical to confirm that your system includes a controller or gateway that allows for grid isolation.
What Is a Backup Load Panel?
Another important piece of the system is what we call a backup load panel. When designing a system for outage protection, not every circuit in the home is always included. Instead, critical loads are selected and placed on a backup panel.
These are the circuits you want powered during an outage, such as:
- Refrigerator
- Lights
- Outlets
- Internet equipment
- Garage door
In larger systems, you may also include air conditioning depending on the system size and battery capacity. The reason for this is to manage energy usage during an outage. Your battery has a limited amount of stored energy, so prioritizing essential loads helps ensure it lasts as long as possible.
Can You Have Whole Home Backup?
Yes, in many cases you can. With larger systems and newer technologies, whole home backup is becoming more common. This means the entire home is powered during an outage instead of just selected circuits. However, this depends on the size of the solar system and the battery and the electrical load of the home. Homes in areas with high electricity usage, such as Palm Desert or Fresno, often require larger systems to support whole home backup. If the system is not sized properly, it may not be able to support all loads during an outage.
Power outages are becoming more common in certain areas due to:
- Grid reliability issues
- Public safety power shutoffs
- Increased demand on infrastructure
Because of this, more homeowners are looking at solar not just as a way to save money, but also as a way to maintain power during outages. A properly designed solar and battery system with an MID device gives you both. It reduces your electricity costs and provides backup power when you need it.
The Key Question to Ask
If you are considering solar and backup power is important to you, the most important question to ask is: Does this system include a controller or gateway that allows it to disconnect from the grid? If the answer is no, your system will not work during an outage. If the answer is yes, then your system has the ability to operate independently and keep your home powered.
Will Your Solar Panels Work During a Power Outage?
If your system is solar only and grid tied, the answer is no. If your system includes a properly designed battery and an MID device that allows it to isolate from the grid, the answer is yes. It all comes down to system design. Solar panels alone do not provide backup power. The combination of solar, battery storage, and the right control system is what allows your home to stay powered when the grid goes down.
Deciding Factors in Residential Solar System Design
Understanding this upfront is critical. Many homeowners assume solar automatically provides backup power, and that is not always the case. If backup is important to you, it needs to be built into the system from the beginning. When it is done correctly, your home can continue running even when the grid is down. Your solar system produces power. Your battery stores it. Your home uses it. And the grid becomes something you rely on less, not something you depend on completely.
To learn more about how solar can work for you, call the Fresno residential solar installers at Supreme Solar.