Black start: What is it and why does it matter?

The electrical grid is designed with redundancy in mind. In order to avoid any consumers losing power, and especially any prolonged drops in power, utilities, and the grid operators have designed backup plans and backups to those backups. Although very rarely, if ever, necessary, the last of those backup plans is perhaps the most important of all: black start resources.

Explaining the concept of black start requires a bit of context about what happens during a major outage event. When the grid is operating normally, there are always more than enough power generation resources and transmission capacity available to meet the need for electricity wherever it is on the system. If a branch falls on one of those transmission lines, or if one of those power plants cannot operate for another reason, there are always backup resources available to pick up the slack.

Utilities and the regional operators of the electrical grid–such as the Independent System Operator of New England (ISO-NE) in the Northeast or the Pennsylvania-Jersey-Maryland (PJM) regional transmission operator in the mid-Atlantic–plan for these contingency scenarios daily, monthly, and yearly. These system operators plan for the worst-case scenarios they can think of and ensure that the grid can continue to serve our electrical needs even under these extreme cases. Implicit within these backup plans, though, is one very important assumption: to keep the grid running smoothly, it needs to continue operating.

Consider, however, a situation in which the entire electrical grid goes dark; this could occur on an island, across a state or region, or even across an entire country. In such a scenario, many power plants would be incapable of turning back on because they need electricity to start and run. As a result, it is necessary for the operators of the electrical grid to maintain resources that are able to start when the rest of the grid goes dark, which can then bring the rest of the grid's resources back online. This is where black start resources come into play.

Though a very unlikely scenario at a large scale, there are scenarios that could cause black start capabilities to be needed at a smaller scale. For instance, when hurricanes cut off electrical supply to many customers in Florida or the Carolinas in 2018, the rest of the electrical grid across the eastern United States continued to operate smoothly.

However, the individual houses and businesses where power was lost needed black start resources in order to get the lights back on sooner than regular electric utility service could be restored. In the case of hurricanes like these, black start resources could have reduced customers' time without electricity from weeks to hours or minutes.

For many electricity customers, black start capability is at most an afterthought: a useful safety net should the need arise, but unlikely to ever truly be necessary. For customers who experience many outages, such as those who live on radial transmission lines, in more rural areas, or on islands like Puerto Rico, having black start capabilities on site can be very beneficial.

There are a number of resources that can provide black start capabilities at the residential level. Certain diesel, propane, or gas generators are capable of turning on without electricity and have long been the go-to option for organizations that can't afford to be without electricity, such as hospitals and emergency response buildings. At a certain point, however, fossil fuel generators run out of fuel, making a renewable resource a great option for providing power when the grid goes dark.

However, solar energy systems on their own are typically incapable of providing energy when the grid is down, even if it's sunny. In order for the components of the system to continue to operate, the system needs to have islanding capabilities. One way to achieve that while also adding black start capability is to pair a solar panel system with an energy storage solution.

Most solar batteries provide black start capabilities, meaning that a house with a solar plus storage system can continue to run at a certain level even if the rest of the electrical grid is out of service.

Interested in learning more about if solar plus storage is right for you? Check out EnergySage's free Solar Calculator tool, which allows you to determine how much you could save by going solar. When you're ready to take the next step in your solar journey, register for the EnergySage Marketplace to request your free solar plus storage quotes from local solar installers.