County of San Diego Zero Carbon Portfolio Plan

Five years since the adoption of the County of San Diego’s groundbreaking Zero Net Energy (ZNE) Portfolio Plan, the County is renewing the plan with a new emphasis on carbon reduction. Subject to funding, this ambitious new Zero Carbon Portfolio Plan aims to achieve a 90% reduction in operational carbon across the County’s 1,000+ building portfolio by 2030, which will be achieved through a combination of energy efficiency, retro-commissioning, monitoring-based commissioning, onsite solar, community choice power purchasing, and building electrification projects.

At a Glance

County of San Diego
San Diego, CA
10.8M SF (1000+ buildings)
  • Strategic Energy Planning
  • Strategic Carbon Planning
  • Zero Carbon Consulting
  • Electrification Studies
  • Zero Net Energy (ZNE) Peer Review
  • Zero Net Energy (ZNE) Modeling
  • Measurement & Verification (M&V)
  • Monitoring-Based Commissioning (MBCx)

The Challenge

Through a long-standing relationship with the County, Stok was engaged to guide the development of the County’s Zero Carbon Portfolio Plan, focused on lessons learned from the implementation of the Zero Net Energy (ZNE) Portfolio Plan as well as the addition of direct carbon reduction measures. Specifically, Stok:

  • Reviewed and benchmarked facility energy data, then translated it into greenhouse gas (GHG) emissions
  • Estimated the potential to reduce carbon emissions through various measures
  • Identified prioritized carbon reduction strategies to shape the Zero Carbon Portfolio Plan
  • Performed building electrification feasibility studies (ongoing)
“Stok was an invaluable partner in developing the County’s 2017 Zero Net Energy Portfolio Plan. The County of San Diego Energy & Sustainability Division is always looking ahead to what’s next, and when we determined the next impactful step would be to address carbon emissions across our portfolio, we immediately thought of Stok to guide us through this new evolution of the County’s portfolio plan. Stok brought a strategic and comprehensive approach to zero carbon, applicable context from intimate involvement in the County’s original Zero Net Energy Portfolio Plan, technical electrification expertise, and deep data processing capabilities that made our portfolio-level decarbonization planning possible. We’re thrilled to continue our close partnership with Stok on the County’s vast portfolio, and this new portfolio plan has set our trajectory toward a zero carbon future that we’re equipped to achieve.”

By the Numbers

Reduction in operational carbon emissions by 2030 (subject to funding)
Annual estimated emissions reduction in 2030 from building electrification alone
Upcoming ZNE projects (7 already completed)

The Solution


To maintain the trajectory of the County’s ZNE Portfolio Plan and strengthen the County’s climate commitments, Stok helped the County identify six core carbon reduction measures that will result in a 90% reduction in operational carbon within Scopes 1 and 2 across the County’s portfolio. These include Green Energy Supply, Energy Efficiency Projects, Proactive Energy Management, Zero Net Energy Building, Renewable Energy, and most notably Building Electrification, which is a new carbon-specific reduction strategy not originally part of the ZNE Portfolio Plan. The team ensured these efforts not only aligned with the County’s previous climate action, but further demonstrated its climate leadership in tackling decarbonization at scale.


Stok led the operational GHG emissions inventory to calculate a baseline and map out reductions on the County’s 2030 target timeline. Gathering energy consumption data from all of the County’s 1000+ diverse facilities, processing it into one format, translating it into equivalent GHG reductions, and mapping it against the County’s timeline, Stok’s deep data processing capabilities allowed the County to accurately inventory its portfolio GHG emissions from which a baseline and annual forecasts could be set—a foundational component of the Zero Carbon Portfolio Plan.


Building electrification is one of six core measures identified in the Zero Carbon Portfolio Plan and one without which zero carbon could not be achieved. To facilitate the transition from natural gas to electricity for space and water heating for kitchen and laundry uses, Stok is performing feasibility studies on all facilities with onsite fuel combustion across the County’s portfolio, starting with the highest users. After identifying existing gas equipment and evaluating historical energy use, Stok works with vendors to identify alternative electric equipment and cost estimates, evaluates what electrical infrastructure changes may be needed, and provides the GHG reduction estimate for the whole project. Stok’s analysis found that just 18 facilities represent 95% of the County’s portfolio natural gas use. To date, Stok has performed electrification studies on eight of these top County buildings, with 11 more planned for 2022.

For more information, dive into the County of San Diego’s full Zero Carbon Portfolio Plan.

Project Leadership

Sandy Houck
Charlie Christenson
Energy Modeling | ZNE | LEED
Michelle Tang