Energy - Residential sales-based electricity costs in nominal and real terms 2006–2023

Changes in the quarterly cost per unit data should be interpreted with care, because:
- the cost per unit of electricity used increases as average electricity demand decreases (and vice versa). This is because some parts of customers’ electricity bills are fixed daily costs.
- if demand in a given period is lower, then the average cost per unit used is higher because the fixed costs are spread across fewer units.

Costs and expenditure figures include GST.

Costs do not include any ownership-based discounts or distributions from consumer trusts. If these discounts and distributions were included, the costs would be lower.

The Ministry has made the following improvements to the sales-based electricity price cost data in July 2014:
- greater consistency of information between retailers. The Ministry now provides more detailed guidance for retailers on what the sales data should and should not include. In particular, the treatment of discounts is expected to be clearer and more consistent between retailers.
- residential costs back to the year ended March 2009 have been revised based on consistent information provided by all electricity retailers. Some retailers have also provided revised data back to the year ended March 2002. This has been incorporated into the residential electricity cost data.
- collecting data more frequently (quarterly, rather than annually) to improve the quality and consistency of information.
- average household electricity expenditure and average electricity demand per household have been added.

At URL provided, select 'Sales-based electricity costs for residential' (Excel file).

The Ministry monitors national residential electricity costs using information about national electricity sales (essentially total electricity sales divided by the quantity of electricity supplied in kWh).

Residential cost data is derived from information obtained primarily from electricity retailers. The Ministry collects the total value of sales, the total volume of electricity sold, and the number of connections.
The residential electricity cost per unit is derived by dividing the dollar value of residential electricity sales by the number of kilowatt-hours (kWh) sold to residential customers.
Cost data reflects any prompt payment discounts actually claimed by customers, as well as multi-fuel and online discounts, incentive and retention payments received, and rates paid by customers on fixed-term plans.
The cost data is based on sales of delivered energy.
The survey also reports the “lines” component of the residential costs. This covers both the distribution and transmission components of the residential costs.
Electricity sales information is collected from electricity retailers on the MBIE Quarterly Retail Sales Survey (Electricity and Gas) return.