NB Power says many meter readers were reassigned to assist with restoration efforts post-Arthur. (CBC)

Some NB Power customers may be surprised by the amount due on their July bills after going several days without power following post-tropical storm Arthur.

The utility says about 30 per cent of its bills will be estimated this month because many meter readers were pulled from their normal duties to join the restoration efforts.

In addition, some meters were damaged or blocked by storm debris and could not be read, while others switched off during the outages.

"Estimated billing is standard practice for utilities when precise readings are unavailable due to extreme weather conditions, emergencies, or other circumstances beyond our control," NB Power said in a statement on Friday.

The estimates are based on usage during the previous month and the same period the previous year, as well as weather conditions.

"NB Power guarantees customers that if a meter was over-estimated, the next bill will be lowered to reflect the customer's actual consumption based on the next actual meter reading," the statement said.

Bills will also be adjusted upward if a meter underestimated consumption.

Normally, only about one per cent of July bills would be based on estimates, the utility said.

Arthur brought heavy rain and high winds to the province on July 5, uprooting trees, downing power lines and causing widespread power outages.

At the peak of the outages, 140,000 NB Power customers were without electricity, with the Fredericton area being the hardest hit with more than 55,589 customers affected.

As of about 6:30 p.m. on Friday, the number of outages stood at 161, with 153 of those in the Fredericton area.