Data and methods
Everything on Elenz is built from public data, almost all of it the Electricity Authority’s market data. These pages set out where each figure comes from, how it is calculated, how it has been checked, and what it can’t tell you.
How the data flows
Three kinds of data, from the newest to the most accurate, are joined into one series on one time axis:
- LiveThe last 7 daysThe EA’s real-time dispatch feed, every 5 minutes, a minute or two after each interval. Updated by a job that runs every 5 minutes.
- RecentThe last 5–6 weeksThe EA’s daily dispatch files: the same dispatch cases, 1–4 days late. They fill gaps in the live feed.
- HistoryBack to August 1997Metered data: what each station delivered and each grid point took, half-hourly, as the market settles it. Final prices throughout.
The history job runs every six hours and picks up each month’s metering as the EA publishes it. History since 1997 explains where the sources hand over.
How each series is built
- GenerationWhat each plant and fuel is generating: the dispatch data for the live week, metered output for history, each unit mapped to its plant and fuel.
- Embedded solarEst.Solar on local networks that isn’t dispatched, mostly rooftops. Nobody measures it as it happens, so it is modelled from installed capacity and satellite sunshine.
- DemandElectricity taken from the grid in each island, with embedded solar added back for underlying demand, and the Tiwai Point smelter on its own.
- HVDC transferEst.Power flowing between the islands on the HVDC link: metered in history, estimated for the live week because the dispatch data doesn’t include it.
- Wholesale pricesSpot prices at the island reference nodes and four more, dispatch prices for the live week and final prices for history, and the figures the Prices tab derives from them.
- Price explainerThe “Why is the price high?” panel on the Now page: what counts as usual, when it is highlighted or opens by itself, and how a possible price setter is found.
- Emissions intensityGreenhouse gas per kilowatt-hour generated, from each fuel’s output and emission factor. Every factor the site uses is listed here, with where it comes from.
- Renewable share and groupingsHow fuels are counted as renewable or fossil, flexible or variable, and how plants are grouped by site, hydro scheme and owner.
- Installed capacityHow much each plant could generate, and when that changed, back to 1997: the basis for the Generation tab’s capacity factors and dispatchable headroom.
- History since 1997How the record back to August 1997 is put together from metered data, the daily dispatch files and the live feed, where the sources hand over, and the known gaps.
- RecordsThe highest and lowest half-hours, months and runs since 1997: which data they rest on, when a record is official or provisional, and what is left out.
Every data source lists all 24 datasets, with what each is used for, how far back it goes, how soon it is published and its licence.
Conventions
- Time
- New Zealand time, NZST or NZDT as it applies on the day. The market works in half-hour trading periods (TP), numbered from midnight: TP 1 starts at 12:00 am. Dispatch runs every 5 minutes; an interval is labelled by its start.
- Units
- Power in megawatts (MW), averaged over each interval. Energy in megawatt-hours: GWh (1,000 MWh) and TWh (1,000 GWh). Prices in $/MWh ($100/MWh is 10 c/kWh). Emissions intensity in g CO₂e/kWh.
- Regions
- New Zealand, the North Island or the South Island. Each island’s figures are its own generation and demand; the HVDC link carries the difference between them.
- Estimates
- Embedded solar and the live HVDC transfer are modelled, not measured. They are hatched on the charts, marked “est.” in the readouts, and embedded solar has an uncertainty band.
- Gaps
- About 7–8% of 5-minute intervals have no dispatch case in either the feed or the daily files. They are filled by a straight line between the intervals either side. Longer gaps in a few series (some price nodes, irradiance) are left empty or shown as zero; the method pages say which.
- Live, Delayed, History
- “Live” means the newest interval is under 15 minutes old; “Delayed” that it is older; “History” that the view is past the live week. The page checks for new data once the next interval is due.
- Longer intervals
- 30-minute, daily, weekly, monthly and yearly figures are averages of the intervals within them, weighted by time. Peaks are the highest single interval or half-hour, not the highest average.
Corrections and code
The EA’s data is used as published, except for a short list of curated corrections: plants not yet in the register, fuels the register has wrong, stations the metered history sees whole, and meters that are shared or net. Each is listed on its method page. The code that builds every figure is public on GitHub, including the corrections (facilities/overrides.toml, facilities/metered_plants.csv) and the analysis behind every constant (analysis/README.md).
Licence and credit
Data from www.emi.ea.govt.nz provided by the Electricity Authority (New Zealand), under CC BY 4.0. Irradiance: Himawari satellite data (JMA/JAXA) and ERA5 reanalysis (Copernicus) via Open-Meteo, CC BY 4.0. Emission factors draw on published figures from Genesis Energy, MBIE, the Ministry for the Environment and the NZ Geothermal Association, cited where they are used. Elenz isn’t affiliated with any organisation, and neither the Electricity Authority nor any other data provider endorses it.
Spotted something wrong, or a better source? Email hello@elenz.co.nz.