By treating everyone with a CD4 count of 350 or less, fewer people would contract opportunistic infections, which require added medicine and healthcare, spokesperson Caroline Nenguke said.
She said fewer infections would improve the quality of life for many people, reduce mortality and reduce new infections.
According to the TAC website, about 97% of people with HIV eventually contract an HIV-related disease like tuberculosis (TB) or pneumonia.
On Friday, Deputy President Kgalema Motlanthe announced that ARVs would be given to everyone with a CD4 count of 350 or less.
Previously, treatment in this category was only open to certain "vulnerable" sections of society such pregnant women and children.
R5bn govt budget
All other patients had to wait until their count was 200 or below before being treated.
Nenguke said a study in Lesotho found that patients who started treatment above a 200-count were 68% less likely to die than those who only started treatment when their count fell below 200.
She said the next step for government should be to offer ARVs to all HIV-positive people with TB, regardless of their CD4 count.
Health Minister Aaron Motsoaledi said the government would budget R5bn for the first year of treatment with another R1bn added in the next financial year.
He said the ARV programme would be integrated into the future National Health Insurance.
About 5.38 million people in South Africa are estimated to be living with HIV, according to a recent Statistics SA report.
The number of new HIV infections for 2011 for those 15-years or older is estimated at 316 900.