The U.S. electric grid is aging. At the same time, it’s becoming more complex.  And extreme weather events, ranging from hurricanes to ice storms to flooding, are becoming both more frequent and more damaging to the grid.

No wonder, then, that power outages are increasing in frequency and severity. And, as more of our society becomes electrified—from electric-powered heat pumps and geothermal systems, to electric vehicles—the impacts of grid outages become even more severe.

According to the best available data from the Executive Office of the President, 679 power outages, each affecting at least 50,000 customers, occurred due to weather events between 2003 and 2012; and these events cost the U.S. economy an estimated $18 billion to $33 billion annually, in addition to damaging key transportation and medical infrastructure that are essential services for much of the nation’s population (3).

This accounts only for weather-related outages—it doesn’t include outages due to non-weather events, which can include fires, earthquakes, falling tree branches, software errors, equipment failures, human error, terrorist and cyberattacks, and animals interfering with grid equipment (squirrels alone account for hundreds of outages per year) (4).

Of course, power outages are most harmful when they occur during a disaster, because they both contribute to the disaster and hinder efforts to provide emergency services when they are most needed. The recent hurricanes in Florida, Texas, and Puerto Rico exposed the vulnerabilities of the electric grid and sparked a nationwide discussion about the implications of power outages for public health and safety.

The disaster in Puerto Rico due to Hurricane Maria is now the largest and longest blackout in American history (5). A month after Hurricane Maria made landfall in Puerto Rico, the majority of the island’s 3.5 million residents still did not have access to power (6).

The hurricane also crippled the island’s $15 billion-dollar pharmaceutical industry, which supplies 10 percent of the United States’ total medicinal production (7). The storm damaged hospitals, knocked out medical refrigeration systems, wiped out internet and phone access, and prevented road access for 100,000 employees.

In addition to all of this, Puerto Rico’s water treatment facilities shut down due to lack of  electricity. This has led to an increase in water-borne diseases, as a quarter of the population was without clean drinking water (8).

If natural disasters continue to become more severe, while nothing is done to improve power systems, the problems exemplified in Puerto Rico will only continue to get worse. Increasing threats from climate change will create more outages to the power system. It is only a matter of time (10).

As noted above, grid outages are not always associated with natural disasters, but when they are, their impacts are compounded. This is because critical services and facilities—emergency shelters, first responders, medical centers, communications and transportation hubs, fueling stations, water treatment plants, refrigerated stores of food and medicines—are subject to widespread power outages too. If these critical facilities are not supported with reliable and long-lasting backup power, they will not be able to deliver emergency services when they are most needed.

Traditionally, backup power for critical facilities like hospitals has been supplied by diesel generators. But several recent disasters have shown diesel generators to be unreliable and prone to failure.

A white paper published by Cummins Power Generation after Hurricane Katrina devastated New Orleans noted that during and after that storm, “many stand-by generating systems located in basements and ground-floor levels failed immediately due to flooding. Generators that were not flooded soon ran out of fuel due to the inability of refueling trucks to deliver diesel fuel. Many other power systems failed to start altogether due to lax maintenance (11).

Similarly, during Superstorm Sandy, nearly 1,000 patients had to be evacuated from New York University’s Langone Medical Center and Bellevue Hospital Center after diesel backup generators failed, plunging the hospitals into darkness. Although both hospitals had located their generators on high floors, critical components like fuel tanks and pumps were in basements, and these basements—despite being reinforced against flooding—were flooded (12).

The U.S. Department of Energy estimated that upwards of 50 percent of diesel generators failed at some time when Hurricane Sandy hit the East (13). The same level of diesel failures has been experienced in Puerto Rico during the continuing blackout after Hurricane Maria hit the island (14).

Fortunately, technology has progressed, and the venerable diesel generator is no longer the best we can do to support critical facilities and vulnerable communities. Battery storage combined with solar PV (solar+storage) provides a flexible and reliable system that scales easily, saves money, and doesn’t rely on fuel deliveries to generate electricity.

Solar+storage systems can be configured to “island” when the grid goes down, meaning they continue to deliver power to their host facility. But unlike diesel backup generators, which sit idle 99 percent of the time, solar+storage systems operate year-round to provide daily benefits, saving money for their owners by lowering electricity bills and, in some cases, generating revenues through the sale of capacity and ancillary services in wholesale electricity markets.

In numerous cases, solar+storage installations have shown that they can pay themselves off over just a few years, well within the lifespan of the equipment (15). By comparison, diesel generators represent a sunk cost that will never deliver cost savings or revenues.

The resiliency performance of solar+storage is not just theory—there are numerous projects with track records to point to. For example, in 2015, a microgrid operated by San Diego Gas & Electric (SDG&E) powered the entire community of Borrego Springs, CA during planned grid maintenance, thus avoiding major service interruptions to the entire community of 2,800 customers (16).

Similarly, a 2012 program to create solar+storage-powered shelters in Florida public schools equipped 112 schools with 10 kW of solar PV and a 40-kWh battery for each, at a cost of $74,000 to $90,000 per school (17). When Hurricane Irma hit Florida in October of 2017, all 29 of the schools that were called upon as emergency shelters were able to self-power using their solar+storage systems. During normal operations, these solar+storage systems lower the schools’ energy costs. Because installed costs for both battery storage and solar PV systems have fallen significantly since 2012, it’s likely that similar systems installed today would be considerably cheaper, and the relative savings greater.

Solar+storage systems can also benefit multifamily affordable housing facilities, which are considered commercial customers by utilities, and often pay extremely high demand charges. Clean Energy Group has analyzed two such facilities in the Boston area, each of which pay more than $80,000 annually in demand charges. A resilient solar+storage system at one of these facilities would add reliable backup power while paying for itself in under six years through demand charge savings alone (18).

Larger solar+storage systems show the same resiliency benefits and cost savings. For example, the Burlington Electric Department in Burlington, VT plans to lease a 1-MW/4-MWh battery to be located at the Burlington International Airport. Combined with an existing 500-kW solar array, the battery should be able to power the airport through an outage with no loss of services to customers. The utility plans to use the battery to reduce its capacity and transmission costs during normal operations, and it expects the system to pay for itself through these savings.

Similar systems have been built in Rutland, VT and Sterling, MA, and more than 100 resilient solar+storage systems are operating or in development across the country (19).