Multifamily Building Design Standard Changes

City Light has recently implemented a new internal design practice for electric service connections of developments with four or more units. These properties will now be required to be served by underground infrastructure.

Frequently Asked Questions (FAQs)

The new internal design practice requires all new developments with four or more units be served by underground infrastructure. This is necessary while Seattle City Light evaluates and establishes construction standards for alternative solutions to meet the growing electric load demand in these developments.

Seattle City Light is adopting a new internal design practice to maintain safe and reliable conductor sizing for anticipated load growth. As electric vehicles (EVs) and electric heating/cooling systems become more common, the demand for electricity in new developments is expected to increase significantly. This new internal design practice addresses these demands by ensuring our infrastructure is sized appropriately to safely accommodate them, supporting the growing need for electrification.

Safety & Reliability

The new standards ensure that the cable and conductor sizing for new homes will meet the expected load demands, thus keeping infrastructure safe and reliable for years to come. New homes will be sized for future electrification, thereby eliminating or greatly reducing the cost of future upgrades.

Shorter Timelines

By providing a clear and consistent framework, developers will be able to plan more effectively, which can reduce service connection timelines and streamline the overall process.

We conduct annual reviews to ensure our service connection standards align with projected load demands, safety protocols, and infrastructure needs. This includes evaluating factors such as acceptable voltage drops, current-carrying capacity, thermal limits, and short-circuit protection, to maintain safe, reliable service.

The new internal design practice is set to be officially adopted on February 10, 2025. It will be included in the 2025 version of the Requirements for Electric Service Connections (RESC).

Once the updated RESC is published, Seattle City Light will follow up with stakeholders through existing communication channels. We will also check in with customers to assess their experience with the new design practice and address any concerns.

For more information or to discuss how these changes might impact your development, please contact City Light’s Engineering Team.

City Light

Dawn Lindell, General Manager and CEO
Address: 700 5th Ave, Seattle, WA, 98104
Mailing Address: PO Box 34023, Seattle, WA, 98124-4023
Phone: (206) 684-3000
SCL_ExternalComms@seattle.gov

Seattle City Light was created by the citizens of Seattle in 1902 to provide affordable, reliable, and environmentally responsible electric power to the City of Seattle and neighboring suburbs.