THE carbon tax has boosted the cost of living scarcely at all. Despite dire talk of an ''almost unimaginable'' increase (Tony Abbott) and $100 for a Sunday roast (Barnaby Joyce) the first official consumer price figures show a far lower impact than predicted by the Treasury.

Last July, Treasury said the tax would push up the consumer price index 0.70 percentage points, adding $9.90 per week to average household costs. In return, households were given compensation averaging $10.10 per week.

But 0.70 percentage points looks like being an overestimate. Inflation figures for the September quarter - the one that encompasses almost all of the electricity and gas price rises - show them adding 0.44 points to the CPI. It's a big figure, but not that much bigger than the usual September quarter slug.

Melbourne households have endured a 13.6 per cent increase in electricity prices - unwelcome but well short of previous September quarter jumps of 19 per cent and 21 per cent.

Nationwide, electricity and gas price rises have added 0.25 and 0.33 points to the consumer price index in the past two September quarters. Treasury expected the gas and electricity price hikes to account for only half of the 0.70 boost, the rest being accounted for by businesses that passed them on.