Wellington's new water entity Tiaki Wai has weighed in amid confusion over new water bills residents received this week totalling hundred of dollars.

Tiaki Wai, which took over from 1 July, sent the first quarterly bill to Wellington region residents on Thursday - with a payment due date of payment 1 September.

RNZ has seen bills ranging between $400 and $900 due in just over a month, with options to set up direct debits on a weekly, fortnightly or monthly basis.

Tiaki Wai chief customer officer Liza Gunn said staff had heard there was confusion over the due date for bills.

If someone had set up a direct debit with Tiaki Wai, they would not have the pay the full, quarterly amount on 1 September, Gunn said.

"...where customers set up direct debits with us, they may pay weekly, fortnightly or monthly instalments against their annualised bill.

"Those with direct debits will not see a sudden in-full payment appear on 1 September - unless they have specified the 'quarterly on invoice due date' option on their direct debit form."

She said payments via direct debit will start from 10 August.

Where customers choose to pay by another method, quarterly payment is due in full by 1 September, Gunn said.

Wellington's mayor Andrew Little said on Thursday the water component of people's rates will be taken out in the next bill, though council rates and water bills will both be increasing this year.

"It is a little bit confusing," Little said.

"Water has come out [of the rates bill], it's been increased, rates have been increased by an average of 5.9 percent, that will be your total picture."