It is hard to give an average price for an alternator repair cost. There are numerous factors that will affect the price. Does the alternator belt just need to be replaced, or is the entire alternator shot? If replacement is necessary, using a rebuilt or used alternator will be much cheaper than a new one. The make and model of the vehicle will affect price as well. Replacing a belt is cheap, and if you can do the work yourself, $35 to $75 should be the average. If a professional does the work you are probably looking at $100 to $125. Replacing the entire alternator will be more expensive. If you are using a new alternator and having a professional do the work, expect a bill between $200 and $500. Using a rebuilt alternator will make the repair somewhat cheaper.