Call them God's waiting rooms or retirement havens, Rosebud and Keilor East are the suburbs with the oldest populations in the greater Melbourne area, the latest figures show.

Keilor East is home to the highest number of people aged 65 to 74, according to a report presented to the Australian Property Council on Wednesday.

The suburb, about 16 kilometres north-west of Melbourne's CBD, is also home to the highest population of 75 to 84 year olds.

However, residents in the Melbourne area don't come any older than the good folk of Rosebud on the Mornington Peninsula.

More than 1300 residents are aged 85, or over in the seaside town.

Based on the lates census figures, their average age is 50.7 years old, almost 15 years older than people living in your average Melbourne suburb. Almost one in three people is aged over 65.

In the next 15 years, however, our elderly are set to migrate north, settling in the semi-rural hamlets of Plenty and Yarrambat.

The Plenty-Yarrambat area will become home to more than 10,000 people aged between 65 and 74 by 2031, the report says.

It will house more than 4000 people aged between 75 and 84 and about 3100 people aged 85 and older.

Yarrambat is named from an Aboriginal word meaning "pleasant views", fitting for those seeking a green-change come retirement.

The figures, compiled by engineering firm Calibre Consulting, are based on 2013 population data and are designed to be used as an indicator of demand for aged care development.

The report, titled Aged Care and Retirement Living Developments, predicts that Melbourne will need 24 new aged care facilities each year until 2031.

"This is roughly the equivalent of 430 new aged care facilities, with an average of 75 places per facility," the report says.

Demand for aged care will increase even further thereafter, said Brent Thomas leader of urban development for Calibre Consulting.

"By 2031, the increase of people aged 85-plus in Melbourne alone will be equivalent to the entire populations of Ballarat or Bendigo," Mr Thomas said.

After Rosebud, the southern and eastern suburbs of Croydon, Bentleigh, McKinnon, Bentleigh East, Highett, Cheltenham, and Brighton were home to the highest numbers of people aged 85 and older in 2013.

By 2031, those suburbs will likely be in the north, around the urban expansion areas of Plenty, South Morang and Epping.

"As Melbourne's population ages, new 'hot spots' of concentrations of elderly people will begin to emerge and in turn, this will re-draw the demographic map of Melbourne," the report says.

It predicts new ageing "hot spots" will also emerge in the west near Bacchus Marsh and generally from Frankston through to Mornington and Rosebud West.

"The pattern is one of an outside ring of elderly, with few expected in the inner city area," the report says.

"This age group is most likely to require aged care opportunities, or associated in-home care and general health, medical and related services."

There are currently 480 aged care facilities, providing beds for 35,399 people, in the Melbourne area including Geelong.

An additional 32,252 aged care places will be needed in the region by 2031. Those places come at a cost of $250,000 each.

That represents a potential $8 billion investment in aged care places by 2031, in addition to the possible demand for retirement living.

"It's not something that we can't invest in, either public or private," Mr Thomas said.

"If you look at the people aged 50 and over in 2051, that will roughly be the equivalent to half of Melbourne's current population.

"So take all of Melbourne today and imagine one in two Melburnians aged 50-plus, and that's the scale of the increase by 2051."

The number of people aged 85 and over in 2051 will almost be equivalent to the current population of Geelong, he said.

Mr Thomas said aged care developers had started to accommodate the elderly and their Baby Boomer children.

"The developments incorporate low care and high care in the same facility," he said.

"It could be an over-50s development, where the sons and daughters move in and then mum or dad is actually high-care facility, which is also located on the same site."

Mr Thomas said the aged care and retirement sector was the only sector in the property market that was not cyclical.

"The demand just keeps going up and up and up," he said.