New methodology

Following queries from users of the data in early 2025 and analysis on how the existing national average fuel price series was performing, we decided to change the data source and method used to estimate this series.

This page outlines what we changed from 7 May 2025, and key differences between the new and old methodology and data reporting. 

Changes to our data sources and methods for calculating retail fuel prices

From 7 May 2025 we began using a more comprehensive data source for fuel pricing.

Our new data source, Datamine, the official data agent for the Gaspy fuel price monitoring app, provides data from over 1500 stations across the country. This provides a better understanding of fuel pricing across New Zealand compared.

Data from the new source is combined with Stats NZ regional population estimates to calculate a national average fuel price.

Like our previous methodology, we then adjust this by comparing it with average fuel prices as derived by Stats NZ for the Consumer Price Index (CPI). The use of the Stats NZ data to adjust our national average fuel prices provides a better measure of fuel prices actually being faced by consumers as the Stats NZ data captures discounting activity through loyalty schemes and shopper coupons. This results in a more accurate measure of retail importer margins.

When the new data series applies

We use this new data source for retail pricing data from 1 January 2022 onwards. This means that all data from this point onwards has been revised as we’ve switched it over to this new methodology.

We’ve chosen this this date to switch to the new data source as there were minimal differences in prices derived by the two data sources at that point.

Series affected 

All series in our weekly monitoring that use national average fuel prices either directly or indirectly will be affected by this change.

The following series are not affected by this change as they do not use national average fuel prices:

• The price of Dubai crude oil in USD per barrel
• The NZD/USD exchange rate
• The price of Dubai crude oil in NZD per barrel
• The importer cost of each fuel type
• The costs associated with the NZ Emissions Trading Scheme (ETS) for each fuel type

Changes to terminology

We have also used this opportunity to standardise some of the terms used in our fuel price monitoring to make it easier for users to understand the data. We now refer to board prices and adjusted prices – more information on these is in the following sections.

Board prices

The board price refers to the price advertised by fuel stations on their roadside price boards. This was previously called the ‘main port price’.

Consumers may pay less than the advertised price and fuel stations by taking advantage of loyalty schemes and discount vouchers.

While we report on the national average board price for fuels, we do not use these in calculating the Goods and Services Tax (GST) component of prices or our importer margins.

Adjusted prices 

The adjusted price refers to the average price paid by consumers for fuel. This differs from the board price for several reasons including:

• Participation in loyalty programmes and use of vouchers
• Regional variation in prices which is not accounted for by our aggregation methods

This was previously referred to as the ‘discounted retail price’. We have changed from this name as our adjustment from the board price covers more than just discounting.

These prices are used for calculating the Goods and Services Tax (GST) component of prices and importer margins.

Changes to the format of our weekly fuel price table

Our previous weekly data series format has grown over time as we have added new fuels and variables.

As part of this review and change in method, we’ve taken the opportunity to reformat the data we publish, and to make it cleaner and easier to use.

Data was previously published in a ‘wide format’, with one row per week and one column per variable. However, each column title had to indicate the fuel, the measurement, and the unit for the value in that column.

We now provide this data in a ‘long format’, with multiple rows per week. This format allows us to better provide information on the fuel, variable measured, and unit of measurement.