1. The Vortec V-8 powered Tahoe Two-mode Hybrid is expected to deliver a composite fuel efficiency improvement of 25 percent when combined with Active Fuel Management™ cylinder deactivation technology.
2. Prius and Corolla are close enough in interior room as to be comparable.... The Prius having the same interior volume as the Camry only matters to the EPA and if you plan filling the interiors with sand.
You can run these numbers using Pruis v. Corolla or Camry v. Camry Hybrid and it still comes out the same.
Over the course of 100,000 miles, the Tahoe Hybrid will save 1,333 gallons of gasoline compared to a non-hybrid Tahoe.
Over the course of 100,000 miles, the Prius will save 856 gallons of gasoline compared to a Corolla. A Pruis would have to get 59mpg combined before it matched the volume of fuel savings of a Tahoe Hybrid.
Over the course of 100,000 miles, the Camry Hybrid will save 769 gallons of gasoline compared to a non-hybrid Camry. The Camry hybrid would have to get 50mpg combined before it matched the volume of fuel savings from a Tahoe Hybrid.
Bottom line... the Tahoe only has to increase it's combined fuel efficiency by 2mpg before it beats the fuel savings of a Camry Hybrid over a standard Camry. Current estimate <15mpg combined + 25% increase> puts the jump more at 3.75 mpg increase.