Parking your car at the airport is notoriously extortionate, but what travellers may not know is that you can make massive savings – in some cases up to 70 per cent – by planning ahead and knowing where to park.

That’s because airport car parks themselves offer big discounts if you book ahead. And you can save even more by parking at one of the private car parks clustered around major airports – most of which will drop you off at the airport with a free shuttle service.

Competition watchdog the ACCC released a report on Thursday that revealed the major airports in Sydney, Melbourne, Brisbane and Perth made a combined operating profit of $280 million on car parking in 2016-17.

Melbourne and Sydney airports made $183.7 million in parking profits alone.

Airport car parks are incredibly profitable thanks to huge profit margins. Sydney Airport’s car park operation, for example, has a profit margin of a massive 72 per cent. That means for every dollar you pay to park your car there, 72 cents are creamed off as profit.

Brisbane Airport’s profit margin isn’t far behind Sydney’s, at 68 per cent. Nor is Melbourne’s, at 60 per cent, or Perth’s, at 52 per cent.

By comparison, supermarkets like Coles and Woolworths – businesses that are genuinely competitive – generally enjoy profit margins of around 5 per cent.

Car parking sites offering the best deals

The New Daily investigated the costs of paying for long-term parking using a four-day period from July 1 to 5.

Sydney costs were by far the most expensive at $200 – comparable to the cost of an interstate flight – but customers could pay half that ($98) by pre-booking online.

Drive-up parking in Melbourne cost $75 compared to $64 for online bookings.

Meanwhile, parking at Brisbane and Perth airports costs $115 and $89 respectively, with bookings lowering the prices to $102 and $72.

By comparison, off-site parking prices ranged between $30 (in Brisbane) to $80 (in Sydney).

The New Daily identified the companies offering the cheapest alternative to on-site airport car parking: Sydney Airpark, Pacific Airport Parking, Budget Airport Parking and Airport Parking 4 Less.

ACCC Chairman Rod Sims advised holidaymakers to plan ahead to maximise the savings as costs can increase the longer you leave booking in your car park.

“Booking online could save you around 20 per cent or more on long-term parking at the airport, while choosing an independent car park near the airport could save you about 40 per cent,” he said in a statement.

The ACCC is concerned about the current regulations which fail to constrain the market power of four of Australia’s major airports, Mr Sims said.

He added: “Unconstrained monopolies often have an incentive and ability to charge excessive prices while lacking strong incentives to improve services.”

Nicholas Enright, director of Compareparking.com.au – a website comparing prices of off-site parking facilities in Australia’s major cities – said he created the site after being personally fed up with costly parking fees.

“The prices have only increased since we started our site and we believe that most Australians can’t afford to park on site for short- or long-term periods,” he said.

“We believe the competition provided by these off-site providers is crucial in keeping the prices of the official airports reasonable.”