An estimated $421m in power transmission reliability investments are on the horizon until 2028, according to Massachusetts-based ISO New England’s regional system plan projects list.

Five upgrades were placed into service in the past few months and no new projects were added, according to the ISO’s latest update.

There are 18 active projects as of this update, including six projects under construction and 12 planned projects.

Nine of the active projects are in Massachusetts and six are in Maine. There is one active project in New Hampshire, one in Rhode Island and one in Connecticut. There are no active projects in Vermont.

Since 2002, the ISO’s work in power system planning has facilitated $13bn in transmission investment, with a total of 879 project components placed into service.

In addition to their primary goal of bolstering reliability, some of the projects have decreased transmission system congestion and prepared the grid for a cleaner future.

Published three times a year, the projects list describes the status of pool transmission facility projects needed to ensure reliability in New England. As a part of the regional system planning process, the ISO (www.iso-ne.com) must continually reassess the timing and components of existing projects to accommodate forecasted changes in net loads, the retirement of generating resources, and the addition or delay of new power resources. And it must study the ability of the New England transmission system to meet federally mandated reliability requirements and adequately serve the region

The ISO’s role in system planning includes seeking input from its planning advisory committee (www.iso-ne.com/committees/planning/planning-advisory). The committee’s open, public meetings provide a forum for stakeholders – including generator owners, transmission owners, government and community representatives, and others – to offer feedback on the regional system planning process.

In addition to helping ensure the region can count on the electricity it needs every minute of every day, transmission system upgrades also help lower wholesale electricity costs and enable the development and use of cleaner energy resources.

Improving the movement of electricity across the region and into areas of limited transmission and high demand can allow more competition among generators, reduce congestion charges in the energy market, reduce the need for expensive generator reliability agreements, and reduce out-of-market generator dispatch payments. It can also allow older, more expensive generators to retire, making way for cleaner, more efficient, less expensive resources.

Because a reliable system benefits all of New England, eligible costs for transmission upgrades are shared across the region, proportionate to an area’s electricity demand. Transmission owners pay for costs that do not offer a regional reliability benefit. One of the ISO’s responsibilities is to determine, through a collaborative and transparent process, whether project costs will be regionalised or localised.

Regional energy trends can affect transmission needs. For example, the New England states are national leaders in energy efficiency policies and programmes. Energy efficiency savings when coupled with new generators and other transmission upgrades may allow the region to defer certain transmission projects deemed necessary to address reliability needs.

With their continued expansion, solar photovoltaic resources and other forms of distributed generation may also one day be able to alleviate or prevent constraints in regional power system transmission or distribution, and reduce or eliminate the need to install new transmission or distribution facilities.

Additionally, market resource alternatives, such as new generators or demand response resources, may in some cases help alleviate transmission needs.