The total - that includes on and off-street parking and penalty charges minus running costs - means it is the third year in a row the figure has increased.
Of the 22 councils, 19 made a profit, with Cardiff (£3.5m) the biggest.
Three councils lost money on parking - Flintshire (£423,000), Blaenau Gwent (£310,000) and Torfaen (£81,000).
Before running costs were taken off, the local authorities had a combined parking income of £35.8m - a 5.6% increase on the previous 12 months.
The RAC Foundation takes official returns given to the Welsh Government by each local authority and analyses them.
Its director Steve Gooding said the figures "up sharply again" could reflect "a recovering economy with people using their cars more".
Earlier this month, the Wales Audit Office said Welsh councils could raise much-needed cash by charging more for services.
However, it cautioned against some rises, citing the potential for increased car parking fees to stop tourists and shoppers visiting town and city centres.
Mr Gooding called for profits made from parking to be ploughed back into transport projects - including the ongoing campaign to tackle potholes.
He said while towns and cities should not be dominated by cars, more than 80% of employees in Blaenau Gwent, Neath Port Talbot and Torfaen rely on their vehicles to get to work -  some of the highest levels in the UK.
Swansea (£2.4m) and Gwynedd (£1.4m) recorded the second and third highest profits, while Monmouthshire's system was the most efficient - with £490,000 spent and £1.42m brought in.

As well as the tech giant, the inquiry centres on Hachette Livre, Penguin, Harper Collins, Simon & Schuster and Verlagsgruppe Georg von Holzbrinck.
The Commission said it would focus on alleged illegal agreements restricting competition in the EU.
The UK's Office of Fair Trading has already carried out a similar inquiry.
The character and terms of agreements that the companies made with agencies are to be examined for breaches of EU rules on cartels, the Commission said.
The Office of Fair Trading has now finished its own investigation, but continues to work closely with the Commission, which is extending the scope of the inquiry across the whole of Europe.
The Commission carried out "unannounced inspections" on the companies in March 2011 as part of its investigations at premises in several European countries.
Apple's iBook store, which supplies e-books to the company's iPad tablet computer and the iPhone, is likely to come under scrutiny.
The EU announced an investigation into Google for potential anti-competitive behaviour in November.
Car parking charges made Welsh councils a combined profit of £13.8m in 2015/16, figures from the RAC Foundation show.
[NEXT_CONCEPT]
Apple and five publishers are to be investigated over anti-competitive practice in the e-book market, says the European Union's anti-trust watchdog.