Do solar panels work during a power outage?

Key takeaways:

• Standard solar panels shut down during outages to prevent backfeeding electricity for safety reasons.

• Solar systems with battery storage can continue powering your home during blackouts by operating in island mode.

• Grid-tied solar panels remain inactive during a power outage regardless of sunlight availability.

Blackouts are annoying. But solar panels should let you harness the sun’s energy during the day even when the grid is down, right? This is actually wrong considering how solar panels work in residential settings. Safety standards require grid-tied systems to automatically shut off when the grid goes down to protect utility workers. Read on to learn why this happens and how you can get security during blackouts with a battery system.

Why solar panels don't work in a power outage

Electrical safety codes like the National Electric Code (NEC) 690.12 for Rapid Shutdown require grid-tied inverters to shut down during outages. This code says solar photovoltaic (PV) systems installed on or in buildings need a mechanism for reducing DC voltage to safe levels during emergencies. It protects emergency responders and utility workers by limiting voltage to specific levels within 30 seconds of power loss.

How photovoltaic cells react in a power outage

Technically, the photovoltaic effect continues to happen even when the panel is disconnected. This means photons from sunlight strike silicon cells and excite electrons inside to create voltage. However, without a circuit connecting it to an electrical load, the panel doesn’t transfer any electric current to your home. The voltage dissipates as heat. If you touch the solar panel, you’ll notice it gets hotter when disconnected from the grid.

This all means that a bright blue sky above does nothing to power your home your neighborhood has an outage (if you have grid-tied solar). You’ll have to wait for the utility company to turn on the power.

What does your solar inverter do in a power outage?

Your solar inverter is like the brain of your solar system. It constantly monitors grid conditions to keep things running safely. When the power goes out, your inverter quickly recognizes the abnormal voltage. But what it does next depends on the type of inverter (and solar system) you have.

Standard grid-tied (string) inverters

String inverters automatically shut down during outages due to NEC 690.12 regulations to protect utility workers. String inverters are the standard type of solar inverter found on many residential roofs. With this setup, the solar panels produce no usable electricity until grid power returns.

Microinverters

While string inverters control a series of panels, microinverters control each panel individually. These also turn off during outages to comply with rapid shutdown safety requirements. Like string inverters, microinverters don’t allow energy for the home during grid interruptions.

Hybrid (battery-ready) inverters

If you have a solar battery with a hybrid inverter, you can continue to charge your battery from the sun during outages. These inverters disconnect safely from the grid during outages but continue powering your battery. Some models also let you use energy from your panels directly during an outage.

Off-grid inverters

These inverters operate independently from the utility grid. Combined with charge controllers, off-grid inverters let you use energy from the sun directly and store the excess in batteries. Since you aren’t connected to the grid, any power outages come directly from your overall off-grid energy setup. You might use a generator to charge your home battery when you’ve had a lot of cloudy days, for example.

Can solar batteries provide backup power?

If you have a battery backup system, you can maintain power for a time after your system switches to island mode. You can customize which circuits receive priority power, which means your essential appliances like refrigerators, medical equipment, and communication devices stay running when you need them most.

A 10kWh battery to power a standard home for anywhere from six hours to a full day. It all depends on how much energy you use. In an outage, you’ll want to make your energy stretch to get the most out of your battery backup. You might consider oversizing your battery to have more security if your area is prone to power outages.

Use a hybrid solar system for reliability

A hybrid system combines solar panels with a battery backup. It’s essentially a cross between grid-tied and off-grid solar. As we mentioned above, a hybrid inverter can let you charge your battery during the day. So, you could factor enough battery storage to last two or three days and then extend that time with sunlight during the outage.

Hybrid inverters automatically detect any grid failures and transition to battery power without you experiencing any downtime. Once utility power becomes available again, your system will synchronize with the grid automatically. No manual intervention needed.

While you'll pay more for the batteries and advanced inverters, you get guaranteed power availability regardless of grid conditions. 

Wrapping up: What to expect in an outage

If you have a standard grid-tied system, it’ll shut off automatically during a power outage. This can be frustrating if you aren’t expecting it, and this might be a reason for you not to get solar panels. You’ll need to get a battery backup system for peace of mind during outages. Many people assume solar panels offer grid independence on their own, but you need batteries to achieve that.

FAQs about solar panels during power outages

Below are a few frequently asked questions about how solar panels work during outages.

What happens to my solar system if there is a power outage in my area?

Your grid-tied solar system will shut down during outages despite sunny conditions. This is because safety systems prevent backfeeding to protect emergency workers. Only battery storage enables off-grid operation when electricity fails.

How long will a solar battery last during a power outage?

During a power outage, your solar battery will last anywhere from six to 24 hours depending on its capacity and your usage. You can stretch this precious backup by running only essentials and benefiting from daytime solar recharging when available with a hybrid system.

Do you need a generator if you have solar panels?

If you have a standard grid-tied system, you can’t generate electricity at night or during outages. You can get a generator for backup power, or you can get a solar battery to store excess energy and use it later.

How much is a solar battery backup?

A solar battery backup can cost anywhere from $6,000 to $25,000 depending on type, capacity, and brand. Some states offer incentives for installing solar with battery backup systems.