Utility-scale battery storage: What you need to know

With the declining cost of energy storage technology, solar batteries are an increasingly popular addition to solar installations. It's not just residential and commercial solar shoppers that benefit from installing energy storage. Utility-scale battery storage is also playing a significant role in the operation of the electric grid, providing cost savings, environmental benefits, and new flexibility.

Unlike residential energy storage systems, whose technical specifications are expressed in kilowatts, utility-scale battery storage is measured in megawatts (1 megawatt = 1,000 kilowatts). A typical residential solar battery will be rated to provide around 5 kilowatts of power. It can store between 10 and 15 kilowatt-hours of usable energy, as with the Tesla Powerwall 2 and LG Chem RESU 10H. A typical utility-scale battery storage system, on the other hand, is rated in megawatts and hours of duration, such as Tesla's Mira Loma Battery Storage Facility, which has a rated capacity of 20 megawatts and a 4-hour duration (meaning it can store 80 megawatt-hours of usable electricity).

Utility-scale storage, or large-scale or grid-scale storage, has historically been provided by resources such as pumped hydro. In a pumped hydro system, a facility will pump water uphill into a reservoir at times when the cost of electricity is inexpensive (in the middle of the night, for instance) and then run that water back downhill through a turbine when electricity costs are higher, and the grid needs extra energy. With declining battery energy storage costs and the increased introduction of renewable energy, batteries are beginning to play a different role at the grid-scale.

The size and functionality of utility-scale battery storage depend upon a couple of primary factors, including the location of the battery on the grid and the mechanism or chemistry used to store electricity. The most common grid-scale battery solutions today are rated to provide either 2, 4, or 6 hours of electricity at their rated capacity. However, it's not unrealistic to anticipate that longer-duration batteries will be available someday soon. Generally, grid-scale batteries are paired with a generating resource, such as a wind farm, or placed on the transmission and distribution system at substations to help balance local electric supply and demand.

Utilities and grid operators often say that utility-scale battery storage is "a new tool in the toolbox," referring to the many ways battery storage can support the grid.

Storage can act like a load (charging from the grid when electricity prices and demand are both low) or like a generator (pushing electricity back onto the grid when demand and prices are both high). Moreover, when power plants take minutes or even hours to turn on, battery storage can inject electricity onto the grid in milliseconds. This level of flexibility from a resource is unprecedented, and the possibilities for harnessing this capability are endless.

Utility-scale battery storage is beneficial when paired with renewable resources like solar or wind farms. While these renewables are fantastic resources for producing affordable clean energy, they can be unpredictable when weather patterns change. Utility-scale battery storage allows resource developers to smooth out the output from these resources, ensuring that renewable energy is injected into the grid when needed.

There are a few primary players in the battery energy storage industry at the utility-scale level. Perhaps the best-known provider is Tesla, whose 100 MW battery in South Australia made waves a few years ago. Beyond this deployment, Tesla has also contributed to the Aliso Canyon storage projects to help alleviate the need for the leaky natural gas facility. The company markets the Powerpack, its original utility-scale storage solution, and the Megapack, a new product designed for even larger-scale applications.

Another major player in the utility-scale battery storage space is AES Energy Storage. Like Tesla, AES also developed a storage project in a couple of months in response to the Aliso Canyon gas facility crisis. Recently, AES announced the groundbreaking of a new 400 MWh battery storage facility in Southern California Edison's service territory, which will be among the most extensive battery storage facilities ever brought online.

A Boston-based company, Enel X (formerly EnerNOC), is a leading global player in the energy storage space. The company has developed storage projects for clients and grid operators throughout North America and recently announced a new storage project in Peru.

Beyond the benefits of installing battery energy storage at the grid scale, there are plenty of reasons to pair one or more batteries with a solar panel system on your property. Though there may only be one grid-scale solar + storage system, these types of installations are increasing in popularity for homeowners nationwide, with tens of thousands of systems installed in California alone over the last few years. If you're interested in participating in the solar + storage movement, register for a free account on EnergySage to receive custom solar or solar + storage quotes for your home.