Summer 2026

An electric vault is a secure, often underground, reinforced enclosure that houses electrical equipment like transformers, switches and high-voltage cables. Utilities like MGE use vaults to safely house electric distribution equipment in dense urban areas where overhead transmission lines and facilities are not optimal for maintenance, public safety or space constraints

Vaults are critical pieces of infrastructure for many new developments in MGE's downtown electric network area. Building them to current standards helps ensure consistency, efficiency and safety for both our customers and our crews.  

What’s changing? 

We have been operating under a draft electric vault standard for the downtown Madison network since 2023. Using input from partners in the architectural, engineering and construction fields, we’ve since updated that standard, which is based on industry standards and best practices. It will become MGE’s final electric vault standard effective June 1, 2027.  

If you are planning a new construction project within our downtown network, the minimum size of the electric vault you need to include in your project is:  

• 1 electric service entrance = 20’ x 25’ vault. 
• 2 electric service entrances = 40’ x 25’ vault. 
• 3 electric service entrances = 60’ x 25’ vault. 
• 4 electric service entrances = second vault location required.

You can find the current map of the downtown network on page 52 of the Electrical Contractors Handbook.  

Why is the standard changing? 

The new larger vault standard ensures safety and reliability as the demand on our electric grid grows. Larger vaults help accommodate increased electric capacity to safely support our customers’ evolving energy needs and our grid modernization efforts for a resilient, future-ready distribution system.

Contact MGE early in the planning process

Engaging with MGE early in the planning process (a minimum of two years before your desired energization date) will help to reduce potential project delays. From the receipt of a completed application, 18 to 24 months is the typical timeline to design, construct, fully populate and energize an electric transformer vault for projects on the downtown network.