A West Auckland landlord was billed nearly four times what he expected for water because condensation on the meter made it hard to read.
The bill comes amid transitional changes to the Auckland Council's ratings system under which some homeowners have received much larger rates bills than expected.
The Herald revealed yesterday that residents who have changed the value of their home miss out on a 10 per cent cap on rates increases as the new system is introduced.
In another change, customers no longer pay for wastewater as part of their Auckland Council property rates.
Henderson landlord Gary Osborne said he was horrified when he got his first bill under the municipal water company's new regional user-pays system.
Bills are now monthly instead of the three- or six-monthly invoices many Aucklanders have been used to.
"My tenants are frugal with water. Then I noticed the consumption figure was an estimate," he said yesterday.
His bill showed readings for consumption at the house of 69 kilolitres (69,000 litres) over 246 days, including summer months - 280 litres a day.
It said estimated consumption over 29 days in August would be 29 kilolitres, or 1000 litres a day.
"Even their own graph of usage history should have given them a clue as to their cock-up," said Mr Osborne, a former maths teacher.
"The bar at the right of the graph is nearly four times the height of the two bars on the left.
"The effect of such a glaring overestimate is to give Watercare an interest-free loan for a month or more - in this case two months."
A Watercare spokesman said the billing team's estimate relied on a previous month's reading by a meter reader, who could not see all the figures properly because of condensation in the meter. It would be checked by a serviceman and Mr Osborne would get a revised bill, showing a more appropriate estimate.
Said Mr Osborne: "They apologised, saying it was human error, but I was bothered by the fuss and the 40 minutes it took me on the phone to sort it out."
Last month, householders received a "transition" bill as Watercare slowly brings customers of the previous local authority water retailers under one system.
From July 1, Watercare increased the price of drinking water by 4c per 1000 litres, or 3.3 per cent, to $1.343.
Wastewater charges have changed too and customers pay a $190 fixed service charge per water meter plus a volume charge of $2.281 per 1000 litres.