The Clean Energy Regulator is due to move into the building after the Department of Climate Change signed a $25.2 million five-year lease last month.
Just 330 regulator staff are moving to the office block in Farrell Place, Canberra, a regulator spokeswoman said, with the rent bill coming to $15,000 per employee.
The building is one of five Canberra offices currently leased by the Department of Climate Change.
It had previously paid $3.7 million a year but department staff are preparing to move to the six star energy rated building Nishi, at a cost of $6.4 million a year.
A spokesman for the Department of Climate Change blamed the rise to $5 million a year on rental increases but said the lease also covered car parking and electricity.