The largest gas supplier in NSW, AGL, has applied for a rise in the regulated gas tariff that could cause average household bills to increase to as much as $1136 a year.

AGL applied for the 20.3 per cent rise citing surging wholesale prices due to the planned export of large volumes of gas from Queensland.

AGL is seeking approval to increase gas prices by more than 20 per cent. Credit:Bloomberg

As a result, the average household gas bill could increase from about $901 a year to $1033 for 2014/15 and as much as $1136 in 2015/16.

The ACT retailer, ActewAGL is also proposing an 18.6 per cent increase for the NSW/ACT border areas while Origin Energy is proposing 20.1 per cent for the southwestern regions of NSW.