Out of all the popular cities in Ireland, Knock is the cheapest city to rent a car in at just $8/day. Renting a car in Knock is 90% cheaper than renting one in Kilkenny where the per day rate is around $80. Other fairly inexpensive cities in Ireland to get a rental car in are: Shannon ($10/day), Cork ($10/day), and Dublin ($11/day). While these cities typically have cheaper prices than the rest of the country, travelers looking to rent a car in Dublin should expect to spend around $11/day on their transportation. The most popular city to rent a car in Ireland is Dublin.