The costs of aerodynamic improvements are associated primarily with the expense of developing a low drag body shape that is attractive and then developing the trim and aerodynamic detailing to lower CD.
The essential inseparability of drag reduction and styling costs makes it difficult to allocate the fixed costs to aerodynamics alone. Manufacturers confirmed that current body assembly procedures and existing tolerances were adequate to manufacture vehicles with CD levels of 0.25 or less.
Previously, aerodynamic styling to CD levels of 0.30 required investments in the range of $15 million in development costs. 36 Requiring levels of CD to be less than 0.25 would likely double development costs owing to the need to stabilize underbody airflow and control engine and internal air flow. Unit variable costs to an automobile manufacturer (from supplier data) are:
- Flush glass windows: $8 to $10 (for four),
- Underbody cover (plastic): $25 to $30,
- Wheel skirts: $5 to $6 each.
Hence the retail price effect (RPE) is calculated as follows:
- Unit investment cost: ~$30,
- Variable costs: ~$48 to $64,
- RPE: ~$125 to $150.
These RPE’s would be associated with CD levels of 0.20 to 0.22, while RPE for achieving a CD levels of 0.24 to 0.25 would not require wheel skirts, reducing theRPEto$90to$115.
Price effects for trucks are expected to be similar to autos, for a similar percentage reduction in drag. Of course, the absolute values of CD will be higher.