Behavior of the firm under rate-of-return regulation with two capital inputs

•The electric utility chooses between inputs for renewable and non-renewable energy.•Two constraints examined: rate-of-return regulation and renewable energy standards.•Rate-of-return regulation decreases the relative investment in renewable energy.•Restructured electricity markets can increase the relative use of renewable energy.•The impact of renewable energy standard depends on rate-of-return regulation. Traditional electric utility companies face a trade-off between building generation facilities that utilize renewable energy (RE) and non-renewable energy (non-RE). The firm's input decision to build capacity for either source depends on several constraining factors, including input prices, policies that promote or discourage RE use, and the type of regulation faced by the firm. This paper models the utility company's decision between RE and non-RE capital inputs. From the model, we derive the result that rate-of-return (ROR) regulation decreases the investment in RE capital relative to the unregulated firm. These findings suggest restructuring electricity generation markets, which removes the ROR on generating assets, can increase the relative use of RE. A second result of the model shows that the renewable portfolio standard (RPS) increases the investment in capital that requires RE as a source of electricity, as expected. This paper contributes to the literature on the substitution between renewable and non-renewable resources, by examining the policies that affect the investment in the two types of technologies. The model can also be applied to other regulated utilities, such as water or natural gas companies, with outputs that are produced from different types of capital.