Incentive programs help overcome the high upfront cost of zero-emission (ZE) vehicle and equipment adoption, and as ZE vehicle and equipment market segments mature, these higher incremental purchase or lease costs relative to conventionally powered technologies are expected to decline. However, price depends on many factors. This white paper focuses on the ZE powertrain components that are drivers of these incremental costs and highlights key factors that play into these costs, such as supply chains. This report will be updated on a periodic basis in support of the publication of the California Air Resources Board’s Appendix D: Long-Term Heavy-Duty Investment Strategy.