Flexible interconnection can optimize the grid and speed deployment of charging infrastructure

Electric truck with charging station

By Casey Horan

As the first blog in this series details, shorter interconnection timelines can be key to accelerating electric vehicle deployments and achieving decarbonization goals.  Luckily, there are currently available policy and technical solutions states can use to achieve timely interconnection, including: (1) hybrid interconnection; (2) flexible interconnection; and (3) ramped connection.  

The process of upgrading the grid can be lengthy, expensive and complex. For utilities, flexible interconnection can help bring down costs by optimizing existing grid infrastructure and deferring costly grid upgrades. Closing the gap between what the grid can accommodate and the scale of the energy resources that can be connected will benefit both utilities and customers. Here, we explore ways states can use flexible interconnection agreements to deploy EV chargers more quickly without putting excess stress on the grid.  

What is flexible interconnection?

The term flexible interconnection covers a range of methodologies for optimizing use of existing grid infrastructure. In the context of EV fleets, flexible interconnection is best understood as limiting the amount of peak power drawn from or injected into the grid, enabling better load management and sizing for make-ready infrastructure deployment. Flexible interconnection can be achieved in two ways: hardware limitations — such as through voltage or wattage restraints, and software limitations — by connecting the distributed energy resources to a system that can adapt power outputs dependent on need and/or constraint.  

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Hardware and software options both have their pros and cons, and there may be some hesitation by utilities to rely on customer-side hardware to respond to power demands. Any concerns over reliability can be assuaged by implementing strict standards like those for solar and storage interconnection in California’s Rule 21. Flexible interconnections are paired with binding agreements to guarantee accountability for both the customer and utility. Moreover, flexible interconnection is easily combined with protocols like managed charging, smart heating and/or cooling, or behind-the-meter resources like batteries to optimize energy usage and use of existing infrastructure.  

Flexible interconnection can be used to keep energy consumption from EV charging below site hosting capacity, i.e., the scale of energy resources the distribution grid can support at any given time. Using flexible interconnection, the total kilowatt hours a customer uses over the course of a day or year stays the same, but the maximum amount of power required for utilities to accommodate the resource without additional grid upgrades is lowered. This way, fleets can install charging infrastructure that utilities would not otherwise be able to accommodate on a shorter timeline without adding excess stress to the grid. 

Utilities can use flexible interconnection agreements to accelerate the interconnection process by accounting for and limiting fleets’ actual charging behavior, which can be monitored and adjusted if and when the need arises, and grid upgrades are in place. Many utilities currently size make-ready, or distribution grid upgrades, based on the cumulative nameplate capacity of customers’ chargers rather than day-to-day energy usage. All electrical upgrades in front of the meter, such as trenching, transformer and distribution lines, are known as utility-side make-ready. In contrast, customer-side make-ready includes everything behind the meter, such as panel and conduit installations.  

Delays may arise on both the customer and utility-side for several reasons. For example, in the last post we discussed the holdups that can happen when a customer is interested in installing multiple resources, and how hybrid interconnection can help speed the process. Flexible interconnection is the logical extension of hybrid interconnection in that it would help overcome some of the holdups and operational constraints fleets face when attempting to install infrastructure that has the potential to exceed a site’s hosting capacity. Furthermore, in areas where make-ready investment is not rate-based, flexible interconnection can save fleets money and defer expensive grid upgrades. 

Flexible interconnection can benefit both fleets and utilities. 

Flexible interconnection provides a dynamic pathway for fleets to get chargers interconnected faster by agreeing to operate below site hosting capacity. For example, if a fleet owner wants to install 10 EV chargers with a collective capacity of 500 kW, the project could be delayed if site hosting capacity is only 400 kW. Rather than delay the project to perform grid upgrades to accommodate 500 kW, the fleet owner could execute a flexible interconnection agreement with the utility to never exceed 400 kW or to limit usage until grid upgrades are completed. Furthermore, accountability can be assured using either software-based or hardware-based tools that limit energy consumption. 

Flexibility will be key to ensuring progress on transportation electrification is both sustainable and scalable. Thankfully, flexible interconnection agreements are just that — flexible. Depending on the situation, agreements can be adapted to serve the needs of both fleets and utilities now and in the future. For example, the hypothetical fleet owner discussed above could agree to more static terms and limit charging to 400 kW across the board. There are also more dynamic possibilities available, such as limiting charging to 300 kW during peak hours while allowing access to the full 500 kW for overnight charging. Thus, the terms of a flexible interconnection agreement will depend on factors that differ by locale and may change over time. 

Flexible interconnection can benefit fleets by getting EV chargers online more quickly and lowering costs. Still, medium- and heavy-duty EVs require significant investment, and fleet owners may be deterred by concerns that their charging hosting site lacks sufficient capacity without additional upgrades. Flexible interconnection could help assuage EV infrastructure investors’ anxieties around host site capacity and make-ready coverage by introducing a more flexible approach to getting EV chargers hooked up to the grid. Over time, this could also save fleets from having to make additional investments to upgrade existing EV chargers when grid capacity increases. 

As the amount of EVs and other DERs on the grid increases, the way states manage them will evolve to include better real-time management of the distribution grid system. This will also require updated planning from the utilities since flexible interconnection tends to require a separation of the grid’s hosting capacity from the quantity and scale of DERs that get deployed. Because this impacts energy usage and load profile, utilities will have to begin factoring this into their planning analyses. For now, states can investigate pathways to pilot these programs by partnering with stakeholders to gather insights on where best to start implementing flexible interconnection. 

States should prioritize addressing barriers to timely interconnection and ensure swift progress toward decarbonization goals. Flexible interconnection is the logical next step to speed EV infrastructure deployment, maximize grid utilization and defer costly grid upgrades.  

Casey Horan is a legal fellow for zero-emission transportation at EDF.

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