Power outages can happen when we least expect them. Severe weather, equipment failure, accidents, and even intentional shutdowns can suddenly leave us without electricity. When the lights go out, we’re often left feeling helpless, unable to power our appliances, charge devices, or even heat or cool our homes.
During these inconvenient and unpredictable blackouts, many homeowners start to wonder: Does solar help with power outages and can solar panels work when the grid goes down? The promise of solar energy is independence from the traditional electrical grid. So can solar panels provide backup power when you need it most?
How solar energy systems work
To understand why grid-tied solar shuts down during outages, it helps to first understand how solar energy systems work under normal conditions.
How solar panels generate electricity
Solar photovoltaic (PV) panels contain solar cells made of silicon that absorb sunlight and convert it into direct current (DC) electricity. The more intense the sunlight, the more electricity the panels produce.
How solar inverters work
The DC power generated by the solar panels passes through an inverter, which converts it into alternating current (AC) electricity that can be used to power your home. Grid-tied inverters synchronize the power coming from the panels with the voltage and frequency of power on the grid. This allows solar power to seamlessly supplement the grid’s electricity.
How net metering works
With net metering, any excess solar power that isn’t used in the home gets fed back into the grid. The homeowner then gets credited for this energy, offsetting the power drawn from the grid at other times.
Why solar may not work during an outage
When the grid goes down, there are two main reasons why grid-tied solar systems also shut down:
Grid-tied systems need the grid
Grid-tied solar systems rely on the grid to function and have no way to supply power without it. When grid power is cut, the inverter automatically shuts down for safety within seconds or minutes. This prevents any electricity generated from feeding back into the downed lines and electrocuting workers trying to restore power.
Safety features disconnect solar
Grid-tied solar systems have an automatic safety feature called Anti-Islanding Protection that disconnects the panels whenever grid power is lost. This protects utility line workers and prevents damage to your solar system. Solar only switches back on once the grid stabilizes.
3 Solutions for solar to work during outages
While grid-tied systems won’t operate during outages, there are solutions that allow solar panels to provide backup power when the grid is down:
1. Storing Solar Energy in Batteries is Key
To provide resilient backup power when the grid fails, a solar system must have a battery bank with storage capacity. Here are two battery considerations:
Battery Capacity Needed
The batteries must have sufficient stored solar energy to power your home’s critical loads when outages occur. Basic off-grid capacity may only support lights and phones.
Backup Power Options
With large battery banks, solar systems can power appliances, HVAC systems, well pumps, and more. Adding a generator as a secondary backup provides extra outage protection.
Pairing solar panels with batteries allows solar energy to be stored and used when needed. Batteries are charged using solar electricity. During an outage, the batteries keep power flowing independently of the grid. These battery backup systems require special inverters that can switch from grid-tied to off-grid mode.
Microinverters are small inverters installed on each solar panel instead of one large inverter for the whole array. During a grid failure, microinverter systems can disengage from the grid while continuing to generate electricity. The energy can then power critical loads when paired with a battery backup.
3. Fully off-grid solar systems
Off-grid solar systems are designed to operate independently, without any connection to the utility grid. Off-grid systems rely on batteries to store solar energy for use when the sun isn’t shining. If sized properly, these systems provide reliable backup power during grid outages. It’s time to become the true hippie recluse!
Maintaining Power During Daytime Outages
Solar panels coupled with batteries can provide clean electricity during daytime power failures. Here’s how:
Direct Use of Solar Power
The sun shining on the solar array generates electricity that can power your home’s loads directly or charge the batteries.
Stored solar energy in the batteries provides steady power as needed, while new solar charges the batteries.
Managing Nighttime Power Outages
Overnight outages present a bigger challenge for solar systems. Here are two ways they can continue providing electricity:
Relying on Stored Solar Energy
The batteries hold surplus solar electricity from daytime production. This charge is drawn down overnight.
Prioritizing Essential Loads
Battery capacity is prioritized for critical systems like lighting, refrigeration, and home medical devices until sunrise.
Do solar panels work on cloudy days?
Yes, solar panels can still produce electricity even on cloudy days, though at a reduced output compared to sunny days.
Here are some key points about how solar panels operate on cloudy days:
Solar cells can convert both direct and diffuse sunlight into electricity. So even though clouds block direct sunlight, panels can still harness diffuse light that scatters off the clouds. On an average sunny day, a solar panel may have 15-20% efficiency. On a cloudy day, this can drop to around 10-15% efficiency.
Solar output on cloudy days depends on cloud cover density. With thin, wispy clouds, production may drop 15-25% compared to a sunny day. With thick storm clouds, output could decrease by 60-80%.
Orientation matters. Tilted solar panels pointed at a cloudy sky can capture more diffuse light than flat panels. Tracking systems rotate panels to follow the sun’s movement, maximizing collection.
While solar panels alone can’t provide power during an outage, with the right battery backup equipment, home solar systems can be configured to keep your most important loads running. By understanding how solar functions and implementing the right technologies, you can take full advantage of your solar investment. Keeping the lights on when the grid goes down provides peace of mind and energy resilience.