Tasmania's Economic Regulator yesterday released an amended price determination for the next 21/2 years after considering the impact of the collapse of the sale of Aurora Energy's customer base.

However, the impact of the revised determination on customers' power bills, which were expected to drop from January 1, won't be known until Aurora responds.

Aurora has until next Friday to submit its pricing proposal, which must be considered and approved by the independent regulator. 

Before the sale process was abandoned, the independent regulator had approved a power price fall of 5.23 per cent from January 1, saving the average household $140 a year and the average small business $650 a year.

The Examiner understands there will be little adjustment to that figure in the first six months, but the regulator has flagged significant changes when unrestricted full retail contestability is introduced from July.

In making its amended price determination, the regulator found Aurora was likely to incur significant costs attempting to retain its existing customers and should be ``compensated for the full costs and risks it will be exposed to under the competitive market''.

That means the cost to serve per customer jumps from $58 to $152 on July 1, which is likely to have a flow-on increase to customers.

``To not take this action may compromise the development of a competitive market and/or Aurora's financial position,'' the regulator stated.