U.S. Energy Projects in Interconnection Queues, by State

By the end of 2023, more than 11,000 energy projects were in interconnection queues in the United States, waiting for a green-light from regional grid operators to proceed with construction. 

This map, sponsored by the National Public Utilities Council, maps out the average age of active energy projects in interconnection queues by state, using data from Berkeley Lab. 

Interconnection Queues, Explained

Interconnection queues are lists of energy projects that have made interconnection requests to their regional grid operators. Once submitted, these requests formally initiate the impact study process that each project goes through before grid connection, forming waiting lists for approval known as interconnection queues. 

In recent years, both the number and generation capacity of queued projects have surged in the United States, along with the length of time spent in queue. 

According to Berkeley Lab, the amount of generation capacity entering queues each year has risen by more than 550% from 2015 to 2023, with average queue duration rising from 3 years to 5 years the same period.  

As a result of the growing backlog, a large proportion of projects ultimately withdraw from queues, leading to only 19% of applications reaching commercial operations. 

The Backlog: Number of Projects and Average Wait Times

Of the 11,000 active projects in U.S. queues at the end of 2023, Texas, California, and Virginia had the most in queue; 1,208, 947, and 743, respectively. 

When looking at the average ages of these projects, all three states hovered around the national average of 34 months (2.83 years), with Texas sporting 28 months, California 33, and Virginia 34. 

Vermont, Minnesota, Wisconsin, and Florida, on the other hand, had the highest average queue durations; 54, 49, 47, and 46 months, respectively. 

Average Queue Duration by Project Type

At the end of 2023, more than 95% of the generation capacity in active interconnection queues was for emission-free resources. The table below provides a breakdown. 

Wind projects had the highest wait times at the end of 2023 with an average age of 40 months (3.33 years). Solar projects, on the other hand, made up more than 40% of projects in queue. 

Overall, reducing the time that these renewable energy projects spend in queues can accelerate the transition to a low-carbon energy future. 

According to the U.S. Department of Energy, enhancing data transparency, streamlining approval processes, promoting economic efficiency, and maintaining a reliable grid are some of the ways this growing backlog can be mitigated. 

All Commercially Available Long Duration Energy Storage Technologies, in One Chart

Long duration energy storage (LDES) technologies can store electricity for 10+ hours, complementing intermittent renewables, boosting grid resiliency, and reducing fossil fuel dependency. 

Created in partnership with the National Public Utilities Council, this chart lists the characteristics of LDES technologies that have commercial or pre-commercial readiness, using data from the LDES Council’s Net-Zero Power report and 2023 deployment update. 

The Four Primary Types of LDES

Before getting into the details, let’s cover the four primary types of LDES. 

1. Mechanical: Stores potential energy (by tension or position) 
2. Thermal: Stores energy as heat
3. Chemical: Stores energy found within chemical bonds
4. Electrochemical (batteries): Stores energy of chemical reactions, where electrical energy is converted to chemical energy and vice versa 

Currently, mechanical storage systems are the most common around the world. Aboveground pumped hydropower, for instance, currently accounts for 96% of all utility-scale energy storage in the United States. 

How Do LDES Technologies Measure Up?

Below, we list the storage capacity, storage duration, and average round-trip efficiency (RTE) of LDES technologies that have commercial or pre-commercial readiness on a global scale. 

For context, RTE measures the effectiveness of a storage system by measuring the ratio of energy output to energy input during a full charge-discharge cycle. Or briefly, the higher the RTE, the lower the losses and therefore higher the efficiency. 

The table above shows that a mechanical, gravity-based LDES system can provide the highest storage capacity while presenting an impressive 70–90% average RTE. 

On the other hand, a chemical power-to-gas-to-power system, which typically converts electricity to hydrogen gas and back to electricity, provides the highest storage duration of up to 1,000 hours. 

With that said, there are different storage needs and siting considerations across electrical grids. Given the diverse range of options available, suitable solutions can be found to complement renewables and aid decarbonization.