Difference between 2002 and 2004 models

BIG TIME

Whole new car.

To start, I would go to KBB or Edmunds and compare the 2002 Prius vs. 2004 Prius.

 

See this for a good overview of the Prius model history and differences between model years.

One clarification: What that article calls Generation III many refer to as Gen II, and what it calls Gen II is often referred to as Gen I. Because the true Gen I (1997-1999) was sold only in Japan, many in the US call the 2000-2003 Gen I. To avoid that confusion, I generally try to specify the year or use the model numbers: NHW10, NHW11, and NHW20.

 

This is the best summary I've been able to come up with...