As our politicians gear up for the general election, many will be considering how much their campaigns will cost.

Analysis of election spending for the last general election and subsequent byelections shows successful TDs spent an average of €18,746 campaigning, equivalent to €2.25 for each first-preference vote received.

It also shows campaign costs differ substantially depending on the size of the constituency, the level of competition and the candidate themselves.

Analysis of the election spend of all Dáil candidates since the 2011 general election shows the most costly campaign was that of Independent TD Noel Grealish, who spent €39,165 getting elected in Galway West four years ago.

However, because not all constituencies are the same or have equal numbers of voters, comparing election spending is problematic. A more instructive comparison is to look at candidates’ election expenses and their expenditure per first-preference vote. This is done by dividing each TD’s election costs by the number of first preference votes he or she received.

By this measure, Mr Grealish’s campaign was the most expensive in the country, equating to €6.29 for each first-preference vote he received.

The Galway West constituency, which incorporates Connemara and Galway city, saw 17 candidates running for five available seats in 2011. It was one of the two most expensive constituencies in which to campaign in that poll, with the combined election expenses of the successful TDs equating to €3.54 per first-preference vote.

In the four-seater Dublin South East, Labour's Kevin Humphreys spent €20,765 on his 2011 campaign, €6.02 for each first-preference vote.

The constituency included high-profile candidates such as Lucinda Creighton and Eoghan Murphy and Labour veteran Ruairí Quinn – all of whom were elected – Chris Andrews (then of Fianna Fáil), economist Paul Sommerville and former Green Party leader John Gormley.

This level of competition contributed to it being the most expensive constituency in which to run an election campaign, with the combined expenses of the successful election candidates equating to €4.38 per first-preference vote.

In the Dublin South West byelection of October 2014, Paul Murphy won a seat running under the Anti-Austerity Alliance banner. He spent €35,064, making it the third most expensive campaign in terms of first-preference votes at the equivalent of €5.36 each.

At the other end of the scale, Independent Mick Wallace spent €9,328 on his 2011 campaign, meaning each of the Wexford TD's first-preference vote cost him 70 cent.

Taoiseach Enda Kenny, who will reach his 40th anniversary as a TD in November, spent just €12,772 on his Mayo campaign, the equivalent of 73 cent per first preference vote.

Other campaigns which equated to less than a euro for each first preference were those of Labour's Pat Rabbitte, who topped the poll in Dublin South West (€0.91) and Sinn Féin's Pearse Doherty (€0.97), whose general election success in Donegal South West came just four months after his success in the 2010 byelection.

The analysis also reveals differences in the amounts spent by successful and unsuccessful candidates.

The average amount spent by a TD elected to the Dáil stood at €18,746, compared with the average of €10,215 for unsuccessful candidates, a figure which includes those for whom no spend was recorded. While 40 per cent of elected TDs spent €20,000 or more on their campaigns, just 15 per cent of unsuccessful candidates had that kind of spending power.

Nine unsuccessful candidates spent more than €30,000 on their election campaigns.

Under the Electoral Act (1997), all candidates, whether successful or not, are required to furnish an election expenses statement to the Standards in Public Office Commission within 56 days of the election. If they are a member of a party, it must also declare any expenses paid on their behalf.

The maximum a candidate can spend on a campaign depends on the number of seats in the constituency. The spending cap stands at €30,150 in a three-seat constituency, €37,650 in a four-seater and €45,200 in a five-seater.

Candidates who have been elected qualify for a reimbursement of up to €8,700. This also applies to unelected candidates who exceed a quarter of the quota in their constituency.

After the 2011 general election, 327 candidates were reimbursed a total of €2.5 million.

If you are viewing this on the app, visit irishtimes.com to search the data.