FACTBOX-Australia's election: how it works

(Reuters) - Australia will hold national elections on November 24, with conservative Prime Minister John Howard hoping for a fifth term in office, and Labor's Kevin Rudd hoping his party can win back power after 11 years in opposition.

The following facts explain how the elections work in Australia.

* Australia has a bi-cameral parliament, based on Britain's Westminster system. The government is formed by the party with a majority in the lower House of Representatives chamber.

* All 150 seats in the House of Representatives will be up for election. The centre-left Labor party needs to win 16 more seats to form an outright majority and win power.

* Going into the election, Prime Minister John Howard's Liberal Party held 74 seats, and governs in coalition with the smaller rural-based National Party, which had 12 seats, and the Liberal-Country Party's one member.

* Voting is compulsory for about 13 million Australians, who must register when they turn 18. Those who don't vote face fines.

* Australia is divided into 150 electorates. Each seat has about 90,000 voters. Lawmakers are elected for a three-year term, although the government can call elections earlier.

* Electorates are based on population, leading to vast differences in size. The inner Sydney seat of Wentworth covers 26 sq km (10 sq mile), while the Western Australian seat of Kalgoorlie covers 2.2 million sq km (849,500 sq mile), an area the size of France, Spain, Germany, Italy, Poland and Britain combined.

* Australia has a preferential voting system for elections to the lower house, with voters marking their ballot papers "1,2,3..." in order of preference.

* If no candidate receives more than 50 percent of the vote, the candidate with the fewest votes is eliminated and votes for them are recounted and distributed to the person nominated as the second preference. This continues until one candidate wins with 50 percent plus 1 votes.

* The voting system means deals between rival parties and independent candidates over preferences can be crucial to the outcome in many seats.

* The upper house Senate contains 76 senators -- 12 from each of the six states and two from each of Australia's two territories -- elected under a proportional system.

* State-based senators are elected for fixed six-year terms, while territory-based Senators are elected for three years.

* Half of the Senate is re-elected at each election. At the November 24 election, 40 Senate seats will be contested, representing six in each state and the four territory Senate seats.

* To win a Senate seat, a candidate needs to gain about 17 percent of the vote in their state. The system helps minor parties and independent candidates.

* Senators elected on November 24 will take up their seats from July 1, 2008.