Date of Award

Spring 5-18-2019

Degree Type


First Advisor

Jim Williams, PhD


An Integrated Resource Plan (IRP) is a tool used by load serving entities (LSEs) to plan how they will meet forecasted energy demand and system reliability requirements through a combination of supply-side and demand-side resources. The goal of an IRP is to identify the lowest cost option to meet future load while also adhering to policy requirements. For Public Service Company of Colorado’s (PSCo) IRP process, a suite of generating resources, storage capacity, and demand-side management programs are all considered when developing a plan that meets state and utility regulatory requirements and environmental targets.

In 2016, PSCo’s system peak demand was approximately 6,600 MW, while energy sales for the year totaled almost 32,000 GWh. PSCo currently operates a fossil fuel-heavy system, with coal accounting for over half of all energy generated in 2016, while the remaining half was a mix of mostly natural gas and wind. While PSCo currently has enough capacity between utility-owned facilities and PPAs to meet this load through 2021, projected load begins to surpass capacity in 2022, a trend which continues through 2050 as utility-owned generation facilities retire and PPAs expire. By 2050, PSCo’s resource position is a deficit of almost 6,000 MW.

This report summarizes an IRP process that considered five future scenarios for the PSCo system. The first is a reference case where existing policy is unchanged, while the others present scenarios where carbon-free or renewable resources are further prioritized. Finally, the alternative scenarios also consider the impact of high electrification in the transportation and building sectors.

Our results show that renewables made up almost 60% of energy sales by 2050 in the Reference scenario, while increasing this value to 90% in the High RES scenarios had only a marginal impact on average retail rates. At the same time, we found that removing the last portion of emissions from electricity generation and becoming 100% carbon-free by 2050 added approximately $645 million to system costs. The results indicate that the electrification of space and water heating and transportation had a dramatic impact on peak load and energy sales for PSCo’s system. By 2050, seasonal peak had shifted from summer to winter, and the daily peak had shifted from afternoon to morning for most of the year.

Due to the high share of variable renewable resources and high curtailment levels projected in our results, we believe that demand-side management strategies (flexible loads, electric fuels, optimal storage use, etc.) will be increasingly important in reducing system costs and increasing capacity factors of renewable resources. The ability of PSCo to manage load and align consumption to periods of renewable generation can significantly reduce the need to build dispatchable resource capacity.