Slingshot and Orcon have been rated as the top broadband providers for the first six months of the year, with Telecom named as also performing strongly.
Epitiro, which offers a range of services to internet service providers (ISPs), released the results this week of tests on Telecom, Vodafone, TelstraClear, Slingshot and Orcon.
Managing director for Australia and New Zealand Michael Cranna said broadband was tricky to measure because the provider did not always have control over all the factors that determined the quality of its service.
Because a range of factors could affect a user's experience of broadband, it was important to understand what actual user experience in the home was, he said.
That approach included the effects of some factors which were beyond the control of providers, such as house wiring, telephone line and modem quality.
"If we have enough measurement points out there in the real world, these factors will average out for each ISP and we'll get a sense of what their services are like to the user, despite these other factors."
Epitiro encouraged people to download its software on to their computers.
That software then ran regular tests on their provider's services.
In the last year, Epitiro had measured providers in more than 12,000 homes all over New Zealand and across different service plans, and believed it had good coverage.
It measured performance for common things users did, like downloading, surfing and gaming.
"We do this on a daily basis, which means we have millions of data points to construct a performance picture from."
Epitiro removed results from plans which were rate limited, as some providers offered those services and some did not.
Orcon's performance was particularly strong in Auckland, where its unbundled services performed well; but it also tended to be a good performer in most other regions of New Zealand.
There was a significant difference between provider performance in regions containing one of New Zealand's large five cities and those that did not, he said.
For example, download speeds outside the "big five" city regions were a third slower than those within them.
Upload speeds were half as fast.
