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Resource Modeling Working Group

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Resource Modeling Working Group

The development of an optimal energy resource mix followed many of the same tenets as Integrated Resource Planning (IRP) or Electric Resource Planning (ERP). This can be thought of as a process of planning to meet customers' needs for electricity services in a way that satisfies multiple objectives for resource use.

Planning for resources typically involves developing and assessing alternative scenarios based on a range of growth rates, resource costs, capital costs, types of generation resources, energy efficiency programs, levels of emissions, water usage and other considerations.

The planning process also involves projecting future needs, assessing the existing assets available to meet those needs and identifying any resource gap so that an electric utility can continue too provide reliable and affordable electricity. The various alternative resource plans can then be compared on the basis of cost, environmental characteristics and other factors.

To tackle this complex process, the Resource Modeling Working Group decided to create an "assumptions" sub-committee. Members of this subcommittee met numerous times in addition to participating in the full working group. After months of work, the group provided industry-specific expertise about resource options and helped develop possible resource portfolio options by vetting assumptions used in the HOMER resource model. The group's findings were included in the February 26, 2013 Study Session Presentation to Boulder City Council


As part of the 2011 work to study the feasibility of forming a city-owned electric utility, the city contracted with Robertson-Bryan, Inc (RBI) to develop a municipalization cost model that compared Xcel Energy's forecasted fuel resource mix, associated costs and resulting greenhouse gas (GHG) emission against several possible resource mix scenarios under a city-owned utility. Staff then performed additional cost model analyses that expanded variables related to interest rates, stranded costs, and acquisition costs (including those associated with SmartGrid City) to explore a reasonable high-case, a reasonable medium-case, and a reasonable low-case for each variable. The results of this modeling indicated that a municipal utility could compete financially with the incumbent utility, Xcel Energy, even assuming the following factors:

  • Higher payments in lieu of taxes (PILOT) and Public Purpose Program Fund investments (e.g., efficiency and conservation and solar rebates)
  • High rate of renewable energy deployment, entirely funded by operating revenues
  • Significant reduction in carbon emissions compared to Xcel's projected fuel mix and Renewable Energy Standard
  • Rate stability with a maximum 4 percent annual increase over 10 years

While these modeling runs were critical in understanding whether a city-owned utility could deliver electricity at or below Xcel's current rates with fewer greenhouse gas emissions, they did not explore a broad range of supply options and evaluate the extent to which a city-owned utility could deliver more renewables cost effectively. Therefore, staff is initiating a more comprehensive resource modeling effort to test actual resource plans, which include transmission constraints and opportunities, reserve margins, and portfolio optimization strategies.


The Resource Modeling Working Group planning effort will be based on various fuel mix scenarios and will look primarily at the following three factors:

  1. Cost and rate impacts associated with various fuel resources mixes (i.e., varying degrees of renewables) using real-time pricing
  2. Resulting GHG emissions associated with various resource mixes
  3. Impacts of load reductions through energy efficiency and local generation

While similar in nature, this early modeling is not intended to replace the full-scale Integrated or Electric Resource Planning (ERP) that will be necessary should Boulder proceed with creating a local electric utility. The resource planning in 2012 and 2013 will use the above factors as a foundational step toward performing a full Integrated Resource Plan (IRP), which will provide the information necessary to develop a municipal energy portfolio.

Some of the planned work effort may (and eventually will) include very specific Power System Analyses to evaluate regional transmission issues such as impacts to critical transmission infrastructure, matching generation and load, maintaining the scheduled interchange with other Balancing Authority Areas and maintaining the frequency in real-time of the electric power system.


The working group met five times in late 2012 and early 2013.

Work Products

Meeting Notes

Working Group Members


Community Members

Tom Asprey – Community Modeling Team
Alison Burchell – Community Modeling Team
David Corbus – NREL
David Cohen – Evolution 7
Brad Davids – Enernoc
Steve Drouilhet – Sustainable Power Systems
Gregg Eisenberg – Eisenberg Energy
Leslie Glustrom – Clean Energy Action
Joshua Kuhn – Community Member
Puneet Pasrich – Colorado State University Ken Regelson – Five-Star Consultants
David Rhodes – Southwest Generation
Debra Sandor – NREL
Andrea Watson – NREL
Sam Weaver – Cool Energy
Ted Weaver – First Tracks Consulting


John Glassmire – HOMER
Peter Lilienthal – HOMER
Nils Tellier – EPSIM Corp

City of Boulder Staff

Heather Bailey – Executive Director of Energy Strategy and Electric Utility Development
Andrew Barth – Communications Specialist
Yael Gichon – Residential Sustainability Coordinator
Jonathan Koehn – Regional Sustainability Coordinator

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