Power lines at sunset.

How To Use Solar Panels During A Power Outage


The nation’s aging electrical grid is struggling in the face of extreme weather. Water shortages from drought reduce hydroelectric power output from dams, and heat waves boost electricity consumption due to increased air conditioner use. Severe storms can cause grid failures due to downed wires, and some utility companies resort to power safety shutoffs to prevent wildfires when conditions are ripe. Unfortunately, blackouts are a growing reality for many Americans.

Yet, our homes are designed to have electricity, and living without it, even for a few hours, can be challenging. As a result, our basements can flood, mechanical systems shut off and home offices become unproductive.

Many households are looking for alternatives to the power grid to keep the lights on, and using solar energy can be an attractive option. However, how you might use solar panels during a power outage depends on both your solar energy equipment and how it’s connected to the grid.

Types Of Solar Homes And How They Handle Outages

Your solar panel system design will determine if and how you can have electricity during brownouts and blackouts. This varies based on whether you have battery energy storage.

Grid-Tied Solar Power: Solar Panels Won’t Work During An Outage

Most solar-powered homes are connected to the power grid and do not have battery storage. Although the solar panels are likely still generating a current during the day during a blackout (unless completely covered in snow), the system will automatically shut down during an outage to protect utility worker safety. The inverter will stop converting direct current (DC) power from the solar panels to alternating current (AC).

Grid-tied systems typically feed surplus solar power to the electrical grid, and the residents receive credits on their power bills in an arrangement known as net metering or net energy billing. However, having electricity fed into the power lines can create unsafe conditions for workers restoring power during an outage.

Therefore, grid-tied solar systems are designed to shut down during blackouts. In fact, the National Electrical Code (NEC) requires the rapid shutdown of photovoltaic inverters.

An Interesting Inverter Option 

There is a model of inverter that can detect a power outage and disconnect the home from the grid. This SMA inverter with Secure Power Supply has plugs so residents can draw up to 2,000 watts of power. This electricity is enough to charge phones, run some electronics or power a refrigerator using solar energy.

However, this grid-tied solar inverter provides electricity only during the day and has no energy storage capabilities. If snow covers the solar panels or there is cloudy weather, the inverter will supply less than 2,000 watts and no power at all at night. Although it doesn’t have all the same functionality as a battery energy storage system, it is usually far more economical to install.

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Off-Grid Solar Power: Power Even During Blackouts

These solar systems are not connected to the electrical grid and therefore are not impacted by blackouts. However, off-grid solar power systems are more costly because they require more solar panels plus battery energy storage.

In many cases, homeowners need to plan their electricity usage around sunny weather or else have a generator to supply electricity when more power is needed for household loads. For example, if the batteries are low and there is cloudy weather, they might not be able to use much electricity.

Often, off-grid homes are located in more remote areas where the electric grid doesn’t reach. Because the home doesn’t have electrical service, there are no energy bills from the utility company. Extending the grid is often prohibitively expensive, making an off-grid solar system an appealing option. Another possibility is having a generator, but they are often noisy and consume fossil fuels.


Grid-Tied Solar With Battery Backup: Keeping Essentials Powered When The Grid Is Down

Grid-tied systems with battery backup are growing in popularity because the cost of advanced lithium-ion batteries has fallen in recent years. Having a solar system with batteries enables you to store excess electricity from the solar panels or grid power. However, when the batteries are full, they can also supply excess energy to the grid, receiving credits on their electricity bills in some areas.

The solar installer can configure the system so that the batteries provide backup power during grid outages. Likewise, the home can also use stored energy when electricity rates are highest (in areas with time-of-use rates), reducing power bills.

Because the system is connected to the electrical grid, it doesn’t usually need as many solar panels or storage capacity as an off-grid solar system. For example, the system doesn’t have to perform well after days of cloudy weather because the home can draw power from the grid.

Unlike solar systems without battery storage, systems with battery backup can isolate themselves from the power grid. This allows homes to use energy from the panels, even during a power outage, without creating unsafe conditions for electrical line workers.

Sometimes, homeowners with existing grid-tied systems and no batteries add energy storage capacity. However, this can be very expensive and sometimes requires replacing the inverter.

The main disadvantage of grid-tied solar systems with batteries is the cost of energy storage capacity. Despite falling prices, battery storage is still quite expensive, and the batteries can have a shorter lifespan than solar panels. However, a 30% tax credit is available for qualified solar energy systems, including the cost and installation of storage batteries. In addition, some states, including California, have additional battery incentives. We recommend you discuss whether you qualify for the tax credit with a tax professional.

How Battery Storage Can Help When Power Goes Out

Whether or not a homeowner decides to install a backup battery system often depends on the energy needs of the residents. Many advanced lithium-ion batteries on the market supply around 10 or more kilowatt-hours (kWh) of backup power. This is enough to keep your lights and refrigerator on, power medical devices and possibly some HVAC equipment.

Often, natural gas or propane heating systems need minimal electricity to operate. However, if a home has electric baseboard heat or air conditioning and an electric water heater and range, it might not be possible to fully power all these loads because they require so much power. Usually, there is a critical load panel, and the residents decide which devices and essential appliances have electricity.

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Solar Generators: Another Option For Power During Outages

Like fossil fuel-powered generators, solar energy backup generators provide emergency power during blackouts. However, they are quiet to operate and use clean energy as a power source. In the last several years, many units have hit the market. Some solar generators are sold as complete kits that include solar energy panels, and others do not include panels.

It’s helpful when sizing the generator to determine what loads you will want to power. For example, you might want to run the refrigerator periodically to prevent food from spoiling or run a sump pump to avoid flooding. Also, some solar-powered generators are relatively lightweight, making them portable and ideal for camping trips.

Simple kits with solar panels start shy of $1,000 but don’t have a capacity under 1,000 watts. More extensive generators without panels begin just under $1,000 and have a capacity of over 1,000 watts, but the final price depends on how many solar panels you add.

The Bottom Line: Plan Ahead To Use Solar Power During An Outage

Although extreme weather is making power outages more common in many places, homeowners have more options for backup power than ever before. Advances in battery technology are making it simpler and easier than ever before to use a solar panel system with batteries for critical loads.

Want to keep your lights on no matter what’s going on with the utility grid? Now is the time to ensure this happens – and you may be able to take advantage of government incentives to reduce the cost of including backup batteries in your solar panel system.

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