Midtown Reliability Project

Tucson Electric Power is helping Tucson thrive by building a stronger, smarter grid that supports our community’s growth, facilitates additional use of clean energy resources and maintains reliability during extreme weather conditions.

The TEP Midtown Reliability Project will support these efforts by reinforcing systems that provide safe, reliable service. It will include a new higher-voltage transmission line, a new substation and other upgrades to modernize our energy delivery systems in central Tucson.

Open House Meeting
Thursday, Sept. 21 | 6–8 p.m.

Doubletree Hotel—Reid Park
445 S. Alvernon Way
Tucson, AZ 85711

More than three times the capacity of current systems

The Midtown Reliability Project will deliver cleaner, more reliable service to customers in central Tucson through the coming generation.

The Midtown Reliability Project will replace older, lower-voltage equipment that cannot keep pace with the increasing energy use in central Tucson, an area that includes historic neighborhoods, popular business districts and the University of Arizona campus. Peak power demand in the area has nearly reached the capacity of that older system, reducing electric reliability and leading to longer power outages on some circuits.

Because the line is urgently needed to maintain reliable service, TEP will seek to complete construction by the summer of 2027.

Components include:

A new transmission line and substation that connect midtown neighborhoods to our modern 138 kilovolt (kV) system, more than tripling electric capacity in the area.
Significant investments in distribution systems that link customers to our local energy grid.
Retirement of up to eight aging substations and other equipment in neighborhoods throughout central Tucson, helping keep our service affordable.

Benefits

Improved electric reliability

The project will complete a 138 kV “loop” around central Tucson, strengthening electric reliability in the area. Power outages would be less frequent and shorter because TEP could supply energy from more than one direction to the substations that support service to residents, business owners, community organizations, service providers and other customers in central Tucson.

Greater capacity for growing energy needs

New 138 kV transmission facilities will provide more than three times the capacity of the current system, enough to meet our community’s day-to-day energy needs for a lifetime.
Aging 4 kV facilities will be replaced with new 13.8 kV distribution lines, poles, transformers and switchgear, improving TEP’s ability to satisfy evolving energy needs.

Greater capacity for customer-owned energy systems

Transmission and distribution improvements will allow customers in the area to continue adding rooftop solar panels, private battery storage systems and electric vehicles. Currently, some central Tucson neighborhoods require additional analysis prior to approving solar interconnections, due to system saturation.

Comparable cost, greater efficiency

Completion of the new, higher-capacity transmission line and associated improvements would allow TEP to retire up to eight 46 kV substations and associated facilities within 10 years, avoiding approximately $42 million in replacement costs for facilities in need of replacement today. Additional 46 kV facilities could be retired in the near future, avoiding these significant additional replacement costs.

Improved service citywide

The Midtown Reliability Project will reduce the strain on TEP’s remaining 46 kV system, helping to avoid overload conditions in other parts of town.

Support for economic growth and a healthy community

The project will upgrade service to the University of Arizona, Tucson’s largest employer, and Banner - University Medical Center’s Tucson campus and emergency room, each of which provides services and benefits for our entire community and supports a growing economy.
Additional energy capacity in central Tucson is needed to support anticipated increases in job and population density described in local municipal growth plans.

Need

TEP’s 46 kV system was designed to serve the energy needs of homes and businesses built in the mid to late 20^th century. While many of those buildings remain, particularly in central Tucson, their energy use has escalated significantly.

Peak energy demand continues to increase in central Tucson and throughout our community. The demands placed on our local energy grid have increased with a growing population, the use of air conditioning rather than evaporative cooling and greatly expanded use of electronic devices.

Some transformers providing service in central Tucson are more than 50 years old, while other elements of our grid in the area are even older. New equipment is critical as residents are currently reliant on equipment rated as being in ‘poor’ or ‘very poor’ condition, creating a greater risk of low voltage and outages. Replacing that equipment would be both costly and ineffective, as it would not address the need for additional capacity in the area.

The Midtown Reliability Project will provide a timely, cost-effective upgrade to these older systems, helping us maintain affordable, reliable service for all TEP customers.

Tucson’s peak energy needs have more than doubled since 1975

The largest proportion of Tucson homes was built in the 1970s. Most of Tucson’s 46 kilovolt system was designed to serve the energy needs of homes and other buildings built in the 1950’s through the 1990’s.

About the Transmission Line

TEP's largest local energy resources are located at our southside Irvington Campus. Our DeMoss-Petrie Substation, near Interstate 10 and West Grant Road, provides a crucial connection point for our remote energy resources.

The Midtown Reliability Project will provide central Tucson with a new higher-voltage connection to these two critical hubs, closing a gap in our local transmission network. That connection would be part of a 138 kV loop that also encircles downtown Tucson and growing southside neighborhoods served by our Kino Substation, which currently has just a single 138 kV connection.

This part of the project, which includes the proposed Vine Substation, was previously known as the Kino-DeMoss Petrie Transmission Line (Kino-DMP Project). Because the line is urgently needed to maintain reliable service, we will seek to complete construction by the summer of 2027.

Updates

TEP has begun a new review of all potential routes for the proposed transmission line, including those previously excluded from consideration as part of the Kino-DMP Project. This will allow us to reengage with area residents and reconsider options, beginning in fall 2023.

In July 2023, TEP defined the study area for the Midtown Reliability Project. It extends to just north of Fort Lowell Road on the north, just west of Interstate 10 and South Fourth Avenue on the west, just south of East 36^th Street on the south and just east of Country Club Road on the east.

Design

The transmission line would be built using steel monopole structures. They will be visually similar to thousands of steel monopoles installed along streets throughout Tucson, and nothing like the wide, lattice-steel structures that are sometimes used for extra-high-voltage (EHV) lines in rural areas.

Most would be about 75 feet tall, with wire spanning about 600 feet between poles. Based on customer feedback, TEP could use shorter poles in some areas by also shortening the span length – a change that would require more poles. We’ll use road right-of-way for placement of most poles.

The estimated cost for overhead construction of the Kino-DeMoss-Petrie line is about $23 million.

Required Approvals

Under state law, TEP must secure a Certificate of Environmental Compatibility (CEC) approved by the Arizona Corporation Commission before it can build the proposed transmission line along an approved route.

TEP will conduct a stakeholder review process before filing a CEC application for the Midtown Reliability Project in 2024. That application will be reviewed by the Arizona Power Plant and Transmission Line Siting Committee in a public process that allows stakeholders to provide comments.

Public Participation

Outreach Materials

About the study area

36,936 residential customers
6,834 business customers
62 neighborhoods
Eight 46 kV substations

About the Vine Substation

The proposed Vine Substation is planned for construction on 1.6 acres along North Vine Avenue just west of the Banner-University Medical Center Tucson staff parking garage. It’s a critical part of the Midtown Reliability Project, which will improve electric reliability throughout central Tucson.

Design

Substations convert higher voltage power to lower voltages for distribution to nearby customers. TEP typically builds open-air substations, but 138 kV substations typically require 5-7 acres of land. Due to the limited availability of suitable building sites in midtown, TEP plans to design and construct Vine Substation as a gas-insulated substation (GIS).

Gas-insulated substations use a nonflammable, nontoxic gas to insulate electrical equipment in sealed conduit, which prevents emissions. While they cost more than open-air substations, they require less space and offer improved safety because circuit breakers and other equipment are enclosed. The substation will include three transformers surrounded by 12-foot masonry block walls.

The estimated cost for the Vine Substation is about $34 million.

Required Approvals and Timeline

Contact

TEP has installed more than 12,000 steel monopoles along City of Tucson streets

Approximately 1,890 of these poles stand 75 feet or higher. Taller poles allow lines to span longer distances – which means fewer poles are needed.

FAQs

How does TEP determine where new transmission lines are needed?

TEP projects future energy needs, including the impact of energy efficiency programs, distributed generation and other factors, to prepare its 10-Year Transmission Plan. The plan describes how we expect to maintain and improve transmission and other facilities over the next decade to satisfy anticipated energy needs and accommodate requests by third parties to interconnect with our system. The plan describes:

Prospective transmission line projects above 115 kV that TEP intends to initiate over the next decade to maintain reliability and meet customers’ future energy needs.
Upgrades necessary to maintain reliable service.
System locations where new transmission facilities may be required.

The plan is filed annually with the Arizona Corporation Commission, which must review and approve individual transmission line projects before construction can begin.

Why doesn't TEP develop transmission lines underground?

It costs much more to build a transmission line underground than to build the same line overhead. The cost difference varies significantly by project but increases dramatically with higher voltages, which explains why many lower voltage lines are installed underground while higher-voltage transmission lines are not. Underground lines also have higher maintenance costs. Because our costs are passed along to customers, TEP avoids unnecessary expenditures to help keep rates as affordable as possible.

Why would it cost more to build and maintain underground transmission lines?

The higher construction cost typically reflects civil engineering expenses, right-of-way acquisition, additional labor, and materials such as conduit, insulated wire and pull-boxes that are not required for overhead projects. Transmission lines conduct energy flows at higher amperages than distribution cables, generating far more excess heat that must be managed to avoid overloads. This requires the use of higher-cost conductors and other insulating infrastructure. Maintenance also costs more, takes more time and requires specialized training for utility workers as well as police, firefighters and others who might respond to an incident involving a high-voltage underground transmission line.

Will these proposed lines produce electric and magnetic fields (EMFs)?

Electric and magnetic fields (EMFs) are part of our everyday environment and have both natural and human-made sources. The earth's magnetic field is one example of a naturally occurring EMF. Power lines and other electrically powered systems that light, cool and heat our homes and businesses, support communications and make other aspects of our modern lifestyle possible also emit EMFs.

For more than 30 years, scientists and researchers from universities, national laboratories, health agencies, the World Health Organization and other groups have conducted research activities into possible health effects of EMFs. According to this large body of peer-reviewed research, there are no confirmed health risks caused by exposure to low-level EMFs. The National Cancer Institute states “Extremely low-frequency EMFs include power lines, electrical wiring, and electrical appliances such as shavers, hair dryers, and electric blankets.”

For more information, please visit our Electric and Magnetic Fields information page.

Is the Midtown Reliability Project part of a new franchise agreement with the City of Tucson?

No. In May 2023, City of Tucson voters rejected a proposal to fund portions of a new midtown transmission line through a fee included in a new franchise agreement between the city and TEP. That proposed line is now part of the Midtown Reliability Project, which will proceed independently from any future discussions about a new franchise agreement. TEP's franchise agreement, which extends through April 2026, authorizes use of public rights of way for our local energy grid.