Most car rental companies have a minimum age of 25 to rent a car without incurring car rental underage fees.
Most corporate owned locations with most car rental companies will allow renters at a lower age with an extra, daily underage car rental surcharge.
While most companies have a minimum age to rent of 21, Rent a Wreck advertises that many of their locations allow renters 18 and over, Hertz rents to 20 year-olds at most locations and FoxRentaCar (opens in a new window) also rents to those 20 and older.
For car rental companies the normal additional daily fee averages $25 - $27 in most US States and ranges from $27 - $35 a day in Canada. (See Exceptions to normal fees below)
Car Rental underage fees (and minimum rental age) can vary from city to city, so it's impossible to get a specific fee amount for an individual rental company.
Enterprise.com (opens in a new window) tends to have the lowest underage car rental fees; they start at $10 per day and go up, depending on the city you rent from.
In the United States, there are also additional exceptions to normal, average underage fee:
New York state : The minimum age for NY is 18 years of age, subject to underage fees from $51 - $72 per day, (depending on the company) and sometimes dependant on age. Rates are generally higher for renters 18 – 20 and on the lower end of the scale for those 21 - 24.
Michigan: For some car rental companies (or specific locations in that state) minimum age is 18 years of age, with an underage fee of up to $45 per day,(depending on the company) and sometimes dependant on age. Rates are generally higher for renters 18 – 20 and on the lower end of the scale for those 21 - 24.
For some car rental companies (or specific locations) no renters under 25 years of age are allowed in Washington, DC or Montgomery, AL
Note Many car rental companies will restrict younger drivers from renting certain specialty and larger sized vehicles, while some charge a larger than normal fee for younger drivers who rent those vehicles.
As with any car rental policy, it is imperative to check directly with the company/location that you want to rent from to determine their particular age requirement and their underage fees.
*Note: Car rental companies can modify policy at any time; I make every attempt to maintain up-to-date info, but always check with an individual company to verify any policy. See: Disclaimer