One of the monuments of Concord, a historic structure that is seen if not exactly admired by tens of thousands of passers-by every day, will undergo some changes in the next year or so.
The monument is the Bridge Street substation of Unitil, the collection of metallic industrial-looking items inside a barbed-wire fence next to the Ralph Pill Marketplace building that is the despair of the city beautification committee but central to the local electricity supply.
This key switching hub in Unitil’s electric system is more than 60 years old, and some of the equipment is being retired as part of what the company says is “routine system modernization.” Another substation on McGuire Street near the state prison will be replaced as part of the project. Construction is expected to be completed by the end of 2026.
Sharply rising demand for electricity, fueled by huge data centers and an increase in electrification, is straining many power systems around the country, but that’s not the driving force behind these projects, said Amanda Vicinanzo, external affairs manager at Unitil.
“Obviously, we’re monitoring what’s going on nationally and see rising demand. But specifically in Concord and across New Hampshire, the growth has been much more steady,” she said. “There’s just a lot of aging infrastructure that has reached the end of its life.”
Few people notice the McGuire Street substation, which sits alongside Unitil’s operations facility for the Concord region, but the Bridge Street facility is hard to miss if you’re driving south on Interstate 93.
Some of the Bridge Street substation’s electric load will be taken over by the new McGuire Street substation, so some of its equipment will depart (those serving 4.16 kilovolts, if you’re curious). But the overall site footprint will stay the same and, considering the strict safety standards that govern high-voltage construction, it’s not as if Unitil can make it much prettier. If you’re not an electrical engineer, you probably won’t notice any difference.
Substations are the electrical grid’s equivalent of exits on interstate highways. They’re the place where electricity traveling at one voltage transitions to a lower voltage in order to travel on different wires, just as Exit 14 enables cars to transition from highway speeds to the traffic snarl that is Loudon Road.
Because electricity travels more efficiently at higher voltages, the transmission lines on big, long-distance pylons are very energized, from 115 kilovolts (that is, 115,000 volts) to 450 kilovolts. Substations reduce this to lower voltage, such as 13.8 or 34.5 kilovolts, to travel on street-level distribution wires. Transformers atop utility poles drop that to 120 or 240 volts for our buildings.
Unitil has about a dozen substations in Concord. Most are pretty small and overlooked but we would notice if they weren’t around. Throughout the state, Unitil has about 78,900 electric customers and 37,300 customers for natural gas.
The McGuire Street work requires permission from the city and is moving through the planning board process. The Bridge Street project is self-contained and does not need city approval.
Building or upgrading substations is one of the stresses facing the electrical system as it struggles to meet growing demand and the changing requirements of renewable power. Components like transformers and switches are in short supply and are becoming much more expensive, which can delay new power supplies from coming online.
