This document discusses methods for estimating costs of novel carbon capture technologies that have not yet been fully developed or deployed at commercial scale. It describes five main approaches: conventional engineering-economic estimates, conventional estimates with probabilistic inputs, applying learning curves, expert elicitation, and providing no cost estimates. The document focuses on the first three approaches. It notes that conventional estimates often ignore uncertainty and guidelines for contingency costs. It provides an example comparing deterministic and probabilistic cost estimates for a pre-commercial membrane capture system. The document also reviews literature on learning rates and discusses applications and limitations for novel technologies. In general, expert elicitation may provide an independent perspective to compare with model-based cost projections.