I'm considering buying my first Prius this year and am trying to determine whether I would be better off financially, in the long run, buying new or used. I've built an Excel spreadsheet to help me but I need your help with it. I tend to pay cash or pay off my cars within 1 year, so I am not taking interest rates into account. LIFE EXPECTANCY: I also normally own a car until it dies. My current 1997 Toyota Corolla has approx. 283,000 miles on it. Therefore, I am assuming a 300,000 mile life expectancy. Is this reasonable? AVERAGE MILES DRIVEN PER YEAR: Between 2002 and 2010, I have averaged 30,761 miles per year. I don't expect this number to change. BATTERY REPLACEMENT COST: My understanding is that the NiMh battery will last approximately 200,000 miles and costs $3,000 to replace. Therefore, I assume I will replace the battery once during ownership of the vehicle. Do these numbers seem reasonable? DEFERRED MAINTENANCE/REPAIR COST: This is what I really need help with from you all. I haven't had a lot of problems with my Toyota Corolla; however, I have spent some money on it over the years with things like a water pump going out, etc. Owning a car for 300,000 miles will eventually result in some repair costs. For the Prius, I am currently estimating this as $4,000 over life of the car. I understand that the 2010 models are expected to have lower maintenance costs, so I assume $3,000 for 2010/11 models. Also, I assume that, for used cars, all of the maintenance costs have been deferred. Therefore, regardless of the year of the used car, I assume the full $4,000/$3,000 maintenance cost. Do you think these numbers are reasonable? The key column on the spreadsheet is average annual cost. Currently, the spreadsheet suggests that "cheapest" avearge annual cost seems to be cars from the 2008 model year costing around $14,000 with around 45,000 miles on them. Also, I'm pretty sure I want the navigation package, so I am limiting my Prius choices to those with the navigation package. Also, I am limiting my model years to no later than 2007. Whether the car is a 2007 or a 2011, I assume they will all make it to 300,000 miles. Any insights you can provide will be appreciated.