Residential consumption trends

Report notes

1. Consumption data in this report refers to offtake from the network and does not include any self-consumed generation behind the meter. The data is received annually or monthly from retailers in the form of monthly EIEP1 files (transferred from retailers to most distributors). These values have not been loss adjusted back to the grid point of connection where energy is reconciled.

2. Residential connections are defined consistently with other reports on EMI - they have no ANZSIC code in the registry. To be clear, this definition means they will include connections that may not be to primary residences, for example holiday homes.

3. Consumption information is cleaned where outliers or data that may not reflect residential use is removed. This involves filtering out ICPs that appear not to be residential given their property name or that have a meter category other than category 1. We exclude any ICPs that use less than 1000kWh or more than 30,000kWh annually. In addition we exclude any ICP using more than 5000kWh in a single month and apply some smoothing. This allows us to calculate an average monthly consumption for various regions. These averages are then multiplied by the full number of residential connections to provide estimated totals for the residential market segment. We include a quality attribute (coverage) in monthly data reports that details the percentage of residential ICPs these consumption statistics are derived from.

4. Distribution summary statistics are available at month, quarter, and calender year time scales. These statistics provide information on the range of consumption across residential ICPs during the period selected. Six distribution summary statistics are provided, the 5th, 25th, 50th or median, 75th and 95th percentiles along with the mean. These summary statistics are based on the set of cleaned data where outliers have already been removed.

5. Trend lines of residential demand as a proportion of regional and national demand are also available under the show parameter. The proportion of national demand is available for all regions types, however, the proportion of regional demand is only available for network based region types (New Zealand, island, and zone). To derive the proportion of demand we have loss adjusted residential consumption back to the root NSP (or grid node) to derive a demand that residential consumption imposes on the system. This provides an apples to apples comparison with reconciled demand and allows us to represent this demand as an accurate proportion of total demand.

6. Temperature can have a significant effect on residential consumption with some years having a warmer or colder winter. This temperature effect has not been adjusted for, so users should consider this when interpreting trends in the data.

7. Time scale adjusts the temporal resolution of the data presented (e.g. by trading period, day, month, year). Although not strictly adjusting the resolution of the data some reports also use the time scale parameter to select specific time segments (like seasons) allowing trends for information for the same time segment to be displayed. For example the trend in average winter consumption.

8. Region types are either network based or derived from standard statistical boundaries. Network-based regions are network supply points (NSPs), network reporting regions, and zones. Mappings are available in the NSP table which is available as a wholesale report. Other regions are derived from ICP location data and statistical boundaries (2013 census). ICPs without location data default to the location of their NSP. Main centres use Territorial Authority boundaries (City Councils) where Wellington includes Porirua City, Upper Hutt City, Lower Hutt City, and Wellington City. Many data reports allow for the selection ‘All regions’ (where the regions are not the data series) to get data for all regions in a single file. Regions are listed in a North to South ordering, except for NSPs which are listed alphabetically.