A study presented to the ACT government in February 2019 said the total cost for a development in the new suburb of Whitlam was $68,600 a dwelling, while a new dwelling along Athllon Drive would cost the government just $8500.

"It is important to note that this study focuses on the cost side of land release and urban planning considerations. It does not examine the value of developed blocks and the potential revenues associated with land release," the study said.

The study, which was released by the ACT government under freedom of information laws, showed it cost the government $57,588 a dwelling in the first stage of Taylor, a greenfield suburb in Gungahlin.

The majority of dwellings in greenfield suburbs are detached houses, while infill sites are generally made up of flats and townhouses.

An infill project of 560 dwellings in Watson cost $20,211 a dwelling, while an infill project of 243 dwellings in Red HIll cost $48,240 a dwelling.

The study said there were generally cost savings from urban consolidation, which reduce the amount government's need to spend to house more people over time.

However, the study warned there was a practical limit to increasing density, with extra costs if too many dwellings require more infrastructure or reduce how attractive the location is to live.

"These issues will need to be considered in devising urban planning or site development strategies," the study said.

The study noted infrastructure costs per dwelling declined as density in an area increased, but "these cost advantages become more marginal between medium and high density sites".

"Infill developments allow for economies of scale for a range of infrastructure types, where additional network capacity is available, and the centralisation of services means that maintenance works are simpler and more cost effective," the study said.

Greenfield dwelling costs in Canberra were lower than Adelaide and Sydney, where each dwelling cost those states about $80,000.

The study was commissioned to inform updates to the ACT's 2018 planning strategy, and also concluded the cost of servicing infrastructure was up to three times higher in new greenfield areas than urban infill locations.

The ACT government expects to add 30,000 extra dwelling sites to the capital over the next five years to meet housing demand in a city that expanded faster than expected.

More than 70 per cent of dwelling sites to be released by the government will be in multi-unit developments.

The government's latest indicative land release program shows 3918 residential dwelling sites would be released to the market in 2022-23, up from 3180 forecast that year in the previous version of the program.

The 2021 census revealed Canberra's population was larger than expected, up 14.4 per cent to 454,000 people since the last count in 2016 and well above the estimated population of 432,000.

The number of dwellings in the second-stage light rail corridor could more than double if planning controls are changed to encourage higher density development, the ACT government has been told.

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A separate study presented to the territory government of the broader light rail corridor area, between Parliament House and Woden town centre, found the area had the capacity for almost 30,000 dwellings.

There are currently 13,100 dwellings and 31,300 jobs in the area, which includes Forrest, Deakin, Yarralumla, Curtin, Hughes, Lyons, Phillip, Chifley, Pearce, Mawson, Torrens and Farrer.

The area in Canberra's south could also sustain up to 86,300 jobs if the planning rules allowed denser development.

By 2041, there could be 22,400 dwellings in the area under a high-density scenario, with an ultimate capacity of 28,900 homes.

The ACT government has repeatedly committed to its urban infill planning strategy while the opposition has sought to guarantee the release of more new land for detached houses.

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