The Senate contains 76 seats and 39 are needed for a majority. 40 seats were contested at this election.
Final results may not be known for a couple of weeks, but projections indicate that neither the Coalition or the Greens will win the balance of power.
Independent Senator Nick Xenophon looks likely to retain his seat, as does the Greens Senator Sarah Hanson-Young, after a close race.
Other Senators could include the Democratic Labor Party's John Madigan, perhaps more than one Senators from the Palmer United Party, Katter Australian Party candidate James Blundell, and potentially Senators from widely unknown parties such as the Motoring Enthusiast Party in Victoria and the Australian Sports Party in Western Australia.
The main point of uncertainty for the Coalition in the Senate centres around Arthur Sinodinos, who is widely tipped to be the next Finance Minister if he manages to beat Pauline Hanson. Penny Wong looks likely to retain her seat for Labor.
Whatever the outcome, the new Senate will not take effect until next July.