SPLTRAK Abstract Submission
Observations of a Colorado Electric-Utility Resource Plan for Increasing Renewables from 55% to 80% by 2030
Ronald A. Sinton
Sinton Instruments, Boulder, CO, United States

In 2019, the U.S. state of Colorado legislature passed a bill to require an 80% reduction in CO2 by 2030 from the major utilities relative to a 2005 baseline. In 2021, one utility proposed a resource plan to accomplish this goal. This talk will present observations on this ongoing process using the treasure trove of technical documentation provided by the regulatory utility proceeding.  Central to the plan are the negotiation of retirement dates for coal plants and the cost and reliability evaluation for new resources including PV, wind, and batteries.  The legislature mandated that a social cost of carbon of $68/ U.S. ton ($0.0748/kg CO2) be utilized in the cost evaluations for new resources including a net present value calculation of the social cost of CO2 emissions. Although the utility uses a capacity-expansion model to evaluate the potential options, the results are seen to be highly constrained by a set of input assumptions on future hourly-demand profiles, coal retirement dates, capacity factors for the coal plants until retirement, and reliability metrics for the variable renewables and storage.  These assumptions became the focus of negotiations during the regulatory process. The areas of particular interest to PV that will be discussed include the pricing that the ratepayers see with respect to the various “kinds” of PV given the different laws and subsidies prescribed for each.  For example, utility PV obtained with a power purchase agreement through an all-source bid is projected to cost $25/MWH, or $35/MWH including transmission.  On the other hand, residential rooftop is compensated at $106/MWH through a net metering approach.  It is noted that hourly demand projections assumed that the greatest source of new load growth, EVs, would be at night. This has the effect of limiting the penetration of PV despite the excellent resource available in Colorado.