When does a project require a medium-voltage electrical contractor?
Most commercial and residential electrical work operates below 600 volts. When a project requires voltage above this threshold — typically 1kV to 35kV — you're in medium-voltage territory. Medium-voltage work requires a licensed electrical contractor with specific training, specialized equipment, and in some states, additional licensing beyond a standard electrical contractor license.
What counts as medium voltage
In U.S. electrical practice, medium voltage generally refers to systems operating between 1,000V (1kV) and 35kV. Common medium-voltage applications include: utility distribution systems (4kV to 35kV), large industrial facilities with on-site substations, campus electrical distribution (hospitals, universities, large manufacturing), wind and solar farm collection systems, EV charging depot distribution, and large data center utility feeds. Above 35kV is high voltage — a separate specialty.
Projects that commonly require medium-voltage work
You'll likely need a medium-voltage contractor when your project involves: a new or upgraded utility substation or pad-mount transformer; underground medium-voltage primary distribution for a large campus or facility; installation of medium-voltage switchgear or motor starters; connection of a large generator (above 600V) to a facility's electrical system; or a utility-scale renewable energy project with a medium-voltage collection system. If your utility company's point of delivery is at medium voltage, everything between that point and your 480V or lower equipment is medium-voltage scope.
Licensing and safety requirements
Medium-voltage work requires specialized training — not just a standard electrical contractor license. Many states have separate high-voltage or medium-voltage endorsements. NFPA 70E arc flash safety requirements are particularly stringent for medium-voltage work, and the personal protective equipment (PPE) and work procedures required are more demanding. Always verify that your contractor's team holds the appropriate medium-voltage safety certifications and that their arc flash hazard analysis is current for your system.
Finding the right contractor
Search for electrical contractors who specifically list medium-voltage or high-voltage experience. Ask for a list of comparable medium-voltage projects and contact those references. Confirm that they have the required specialized equipment (high-voltage gloves, live-line tools, specialized test equipment) and that their crew holds current NFPA 70E or equivalent training. For large projects, request that the contractor provide a project-specific arc flash hazard analysis.
Published · ElectriScout Editorial