(NerdWallet) – When it comes to saving money on rental cars, there’s no shortage of advice. Some suggest skipping mainstream companies and using a car rental alternative, like a peer-to-peer car-sharing service. Others promote package deals through online travel agencies like Expedia. And then there’s this advice: Rent through a rental car company’s downtown location, rather than at the airport.

So how much do you really save by booking an off-airport car rental? Are airport rental cars more expensive? Turns out, it’s about 26% more expensive to rent a car at the airport versus at its downtown counterpart.

That’s according to a NerdWallet analysis conducted in March of 360 rental car prices (including taxes and fees) across America’s 20 largest airports. The study compared the price of a weeklong rental at eight major car rental companies against the cost to rent at their nearby downtown counterparts.

How much money you actually save with an off-airport car rental

NerdWallet found that weekly car rentals for downtown locations were, on average, $126 cheaper than airport locations. That is, you can expect to spend about 26% more for an airport rental compared to a downtown rental.

For rentals longer than one week, expect even more savings.

Why are airport car rentals so much more expensive?

The price difference might not just be the car rental companies trying to take advantage of weary air travelers. Generally, the car rental companies aren’t even the ones pocketing most of the 26% excess.

Most airports charge rental car companies to operate on their site. Fees vary by airport, but they are often intended to cover costs that the airport fronts, such as shuttle, cleaning and security services. Sometimes, airports simply say this fee covers the right to do business.

For example, San Francisco International Airport charges rental car operators 10% of gross receipt revenue from airport customers. SFO also charges a $16 transportation and facility fee per signed rental car contract.

Besides airport-imposed fees, some states levy tourism fees on cars rented from hotel and airport locations (which doesn’t necessarily apply to cars rented at stand-alone locations).

Most rental car companies pass these costs on to renters.

Benefits of booking a rental car off-site (beyond savings)

Savings on the sticker price aren’t the only reason to book a rental car off-site.

You might save time

Just because a rental car is listed as “on-site” at the airport doesn’t always mean you can walk straight from your gate to the rental car counter. Some airports have a shuttle ride to the rental car facility. Once there, you might be greeted by a long line at the rental car counter, especially if multiple big flights just landed. If shuttle frequency is limited, it might be faster hailing a cab and renting downtown.

You’ll pay only for the days you need a car

Depending on the nature of your trip, you might need to rent a car for only a few days. Say you’re headed to Colorado, where you plan to spend a couple of days downtown in Denver before driving out to the Rocky Mountains.

If you’re flying into Denver International Airport, you could pay $10.50 to take the Denver airport rail to Denver Union Station. Say you were staying at The Westin Denver Downtown, which is just a 10-minute walk from Union Station. It charges $35 per day for parking (and $46 for valet).

By picking up your rental car downtown the morning that you drive off to the Rockies, you could not only avoid paying for unnecessary rental car days in what’s otherwise a fairly public-transit-friendly and walkable city — but you could avoid parking charges, too.

You can maximize rideshare discounts on days you don’t need a full rental car

If you go part of your trip sans car — or you end up taking a rideshare to an off-site rental car location — here are ways you can save on rideshares (or at least earn some rewards).

Lyft has partnerships with Delta Air Lines and Hilton, where you can earn either Delta SkyMiles or Hilton Honors points based on your fare’s cost. Pay for your Lyft with certain Chase credit cards and earn up to 10x bonus points or as much as 5% cash back.

Meanwhile, certain American Express cards offer a monthly Uber Cash benefit, which can be used toward Uber rides or U.S. Uber Eats orders. Terms apply.

When to skip the downtown rental

Despite the savings, booking cars off-site might not always make sense. Being able to pick up your car immediately upon landing might be more convenient — and convenience might easily be worth the extra cost. Here are a few other reasons to skip the downtown rental:

  • Some downtown locations have limited hours. While airport locations are often open 24/7, it’s not uncommon to see the downtown location closed on Sundays, or with fewer operating hours (such as a closing time of 4 p.m.).
  • You still need to find a way downtown. If there’s no free hotel shuttle or easy public transit downtown, then you might also have to pay for a taxi or rideshare, which can eat into your savings. NerdWallet’s study also analyzed average Uber and Lyft fares between airports and downtown. The average Uber fare was $28.21 each way, while the average Lyft fare was $22.86.
  • Downtown locations aren’t always cheaper. While they’re generally cheaper than their airport counterparts, the trend isn’t always true. If your travel is flexible, compare prices before booking.

How to find a cheap airport rental car

If you are going to book a rental car from the airport, there are a few tricks:

  • Look to the cheapest rental car companies. Another NerdWallet analysis of prices by rental car companies found that Enterprise, Budget and Hertz round out the top three cheapest rental car companies, on average.
  • Try booking at the last minute. While a bit more of a gamble, procrastinating can sometimes save you money. NerdWallet found that rental car prices tend to be cheaper when booked one week in advance of the reservation date versus three months in advance.
  • Look to rental car loyalty programs. Most major car rental companies have accompanying loyalty programs that can earn you free rentals and upgrades. For example, while National is among the most expensive rental car companies, its National Car Rental Emerald Club is among the best, with benefits like a free car rental day for every five qualified car rentals made by members with Emerald Club Executive Elite Status. They also receive benefits like complimentary private airport delivery.

JT Genter and Sam Kemmis contributed to this report.