TONY Abbott said its impact on the cost of living would be ''almost unimaginable''. Joe Hockey said it would ''drive up the price of everything''. Nationals Senate leader Barnaby Joyce said it would force working mothers to pay ''over $100 for a roast''.

Yet the first figures in on the price impact of the carbon tax show its effect contained and inflation low.

The privately compiled TD Securities Melbourne Institute price index barely moved as the carbon tax came in in July. The total increase for the month was 0.2 per cent, taking the annual rate of inflation to just 1.5 per cent, the lowest in three years.

TD Securities' findings aren't because energy prices didn't rise. It reports a jump in electricity prices of 14.9 per cent and a jump in household gas prices of 10.3 per cent, almost all of which would have been due to the carbon tax. But the little-appreciated reality of consumer spending is that by themselves electricity and gas aren't very important in household budgets. Combined, they make up 2.7 per cent of consumer spending. In contrast meals out and takeaway food account for 5.5 per cent and alcohol 4.8 per cent.