The FTSE 100 firm said it would impact profit by about 2.5 per cent.
Aggreko, which provides power generators and temperature control equipment, posted a revenue jump of 22 per cent from 1 July to 19 October, boosted by its £59m Olympics contract.
Capital expenditure would be less in the first half of 2013 than for 2012 as economic outlook weakened in many of its markets, it said.
"Overall, trading continues to run broadly in line with our expectations," the company said in a statement today.
"Despite the increase in bad debt provisions during the year and unusually high mobilisation costs, we expect that group margins for the year as a whole, both on a reported and underlying basis, will be at similar levels to last year."