Auckland Transport said it was currently in negotiations and until these were completed it could not quantify savings.
"Quite simple, if it is not financially beneficial it will not happen," Auckland Transport said in a statement.
About half of Auckland Transport staff are located at Henderson and the remainder across multiple buildings in the central city, Takapuna and Manukau.
It has looked at 26 properties and said the building under consideration was the cheapest shortlisted option.
Another CCO, Development Auckland, is investigating the longer-term options for the Henderson site, the headquarters of the former Waitakere City Council. Options for the site include housing, commercial and retail space.
Auckland Transport says most of its business was with the likes of Auckland Council, New Zealand Transport Agency and suppliers predominantly in the central city.
Reports had highlighted the inefficiencies of being across multiple sites and productivity gains if most staff were located near the CBD in one building.
Waitakere councillors Penny Hulse and Linda Cooper are relaxed about the possibility of Auckland Transport leaving Henderson, which is earmarked for major development under the Unitary Plan.
Ms Cooper said Auckland Transport's accommodation plans had been known for some time.
"Auckland Transport hasn't provided for any new jobs locally and most of the staff coming from places like Howick and North Shore call its 'Horrenderson' and can't get out of there fast enough".
She said Auckland Transport leaving would create some exciting opportunities for the site.
"What Henderson cries out for as a metro centre is more people living at its centre...the council as a large land owner can be instrumental in attracting development partners to building those much needed homes for young families and older couples wanting to downsize," she said.
Ms Hulse said it would be pretty disappointing if Auckland Transport moved out of Henderson, saying the council would need to get on and move Henderson up the list of town centres to be upgrade.