Future energy system transitions could substantially increase material demand, but material supply might lag, suggesting implications for the scale and pace of energy technology deployment. We develop a new capability in the Global Change Analysis Model to endogenously quantify demand for 12 materials—including critical minerals—in the power sector and evaluate the impacts of material supply availability on power sector evolution. If future supplies of the 12 materials in the global power sector are constrained by historical growth rates, investments in the global power sector through 2050 reduce by 12% and 2050 electricity prices worldwide increase by 14%–41% relative to an unconstrained supply case. Intensified impacts on investments (−34%) and electricity prices (50%–101%) are observed in a low-carbon transition (RCP1.9) scenario, which may be alleviated with material supplies growing at three times historical rates. Technological innovation that reduces material intensities could also mitigate these impacts.