More than 1.5 million people have now completed their census papers online.
Statistics New Zealand has delivered more than six million survey forms for today's census.
A spokesperson for Statistics Minister Maurice Williamson says it is now expected that 2 million forms will be lodged through the internet.
Only 390,000 survey forms were done via the internet in the 2006 census.
Census organisers earlier said they were confident the census website would remain operational all day, despite heavy demand.
Census spokesperson Vikki Carter says the website is designed to handle 200,000 visitors an hour.