Records

The 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.

Shown on Records and Now Checked against the code 17 October 2026

Data used

Real-time dispatchElectricity Authority (EMI) The live week: generation by unit, island load, prices, the Tiwai smelter (TWI2201). Also the inputs to the HVDC estimate and the price explainer.The last month or so · Usually 1–2 minutes after each interval starts
Dispatch prices and volumesElectricity Authority (EMI) Fills gaps in the live week; history for the weeks since the latest metered month; plants the metering doesn’t have (batteries, new solar farms).From 10 Sep 2020 · 1–4 days late
Final energy pricesElectricity Authority (EMI) Every price in the history. The usual prices the explainer compares with.From 1996 (the site uses August 1997 on) · Usually the next day
Metered generationElectricity Authority (EMI) Generation by plant and fuel for every month it has been published.From Aug 1997 · About 5–6 weeks after each month
Embedded generationElectricity Authority (EMI) Stations on local networks before 2009, and their gross output where Generation_MD records it net of local load.From Oct 1998 (most points from Apr 1999) · About 2 weeks after each month
Grid exportsElectricity Authority (EMI) Demand in history.From Oct 1996 · About 2 weeks after each month
Grid importsElectricity Authority (EMI) Demand in history.From Oct 2000 · About 2 weeks after each month
Grid exports to TiwaiElectricity Authority (EMI) The smelter’s load in history.From Oct 1996 · About 2 weeks after each month
HVDC flowsElectricity Authority (EMI) HVDC transfer in history; the fit behind the live estimate.From Oct 1996 · About 2 weeks after each month

What counts as a record

The Records page keeps the highest and lowest values in the history since 1 August 1997, for New Zealand and for each island. There are three kinds:

Half-hour records: The highest or lowest half-hour: each trading period’s average, as the history holds it. A record has to beat the one before it; equalling it doesn’t count.
Month records: The highest or lowest calendar month (New Zealand time): the renewable share of the month’s generation, and the month’s wind generation in GWh.
Runs: The longest unbroken run of half-hours meeting a condition, joined across month boundaries: at least 90% renewable, prices under $5/MWh, or no Huntly Rankine running.

Each record’s page shows how it grew: every time it was broken since 1997, worked out from the half-hours that beat everything before them.

Official and provisional

A record is official once it rests on final data. The history uses the EA’s metered generation and demand for every month it has published (about 5–6 weeks after the month ends), final prices (usually the next day) and metered HVDC flows (about two weeks after the month). See History since 1997.

Anything newer comes from dispatch data, the market’s 5-minute targets. Records set there are provisional: shown as such, with when the metered data is due, and confirmed or dropped when it arrives. Dispatch runs 1–2% above metered generation (wind about 3.5%), so a provisional record that only just beats the old one often doesn’t survive. The page says which way it went for 30 days.

The Now page checks the live week itself: when a half-hour of the live data beats a record for generation or demand, a line under the price tiles says so. Prices and HVDC are left to the history: live prices are dispatch prices, which can be far from the final ones (on 9 August 2021 dispatch prices peaked at $356,621/MWh, final prices at $2,698), and live HVDC is an estimate.

A record is marked New for 30 days after it first appears in the official records.

Every record

Definitions follow the rest of the site: generation is each fuel’s output summed (battery discharge only, no HVDC); the renewable share is of that total, with geothermal, bioenergy, hydro, wind, grid solar and embedded solar counted as renewable (Renewable share and groupings); fossil generation is Huntly’s Rankines, gas, diesel and waste heat; demand is metered grid demand (Demand); prices are at the island reference nodes, Haywards and Benmore, and New Zealand’s is the higher of the two.

Record	Kind	Kept for	Official with
Peak demand Highest half-hour of grid demand	Half-hour	New Zealand, each island	Metered generation and demand
Peak demand without Tiwai The aluminium smelter’s load taken out	Half-hour	New Zealand, South Island	Metered generation and demand
Lowest demand Lowest half-hour of grid demand	Half-hour	New Zealand, each island	Metered generation and demand
Highest renewable share Half-hour	Half-hour	New Zealand, each island	Metered generation and demand
Highest renewable share Calendar month	Calendar month	New Zealand, each island	Metered generation and demand
Lowest renewable share Half-hour	Half-hour	New Zealand, each island	Metered generation and demand
Lowest renewable share Calendar month	Calendar month	New Zealand, each island	Metered generation and demand
Longest run at 90% renewable or more Every half-hour in a row	Run of half-hours	New Zealand, North Island	Metered generation and demand
Lowest fossil generation Rankines, gas, diesel and waste heat	Half-hour	New Zealand, each island	Metered generation and demand
Longest with no Huntly Rankine running The coal and gas units at Huntly	Run of half-hours	New Zealand	Metered generation and demand
Peak wind Half-hour	Half-hour	New Zealand, each island	Metered generation and demand
Windiest month Wind generation in a calendar month	Calendar month	New Zealand, each island	Metered generation and demand
Peak grid solar Solar farms the market dispatches	Half-hour	New Zealand, each island	Metered generation and demand
Peak embedded solarEstimate Rooftops and small arrays, modelled	Half-hour	New Zealand, each island	Metered generation and demand
Highest price Half-hour, final price	Half-hour	New Zealand, each island	Final prices
Biggest gap between the islands Haywards against Benmore, half-hour	Half-hour	New Zealand	Final prices
Longest run of near-zero prices Under $5/MWh (New Zealand: both islands)	Run of half-hours	New Zealand, each island	Final prices
Most sent north Benmore to Haywards, half-hour	Half-hour	New Zealand	Metered HVDC
Most sent south Haywards to Benmore, half-hour	Half-hour	New Zealand	Metered HVDC

What is left out, and known limits

Days the clocks change. Some of the EA’s older metered generation files (1997 to at least 2005) number those days’ half-hours by the clock, 48 of them, where the history counts straight through the change (46 or 50). Generation there is missing for two half-hours and an hour out after the change, so those days are left out of the generation and demand records, and runs carry on over them rather than break. Prices and HVDC are unaffected.
Embedded solar is modelled (Embedded solar), so its records are estimates, and it counts towards the renewable share as it does everywhere on the site.
Coverage. The history has gaps (a few stations missing for some months; see History since 1997). Totals before 2009 leave out embedded stations the tracker doesn’t show later.
The South Island has no fossil plant, so its renewable share is always 100%; those records are shown as a note, not a date.
Huntly’s Rankines can burn coal or gas without the market seeing which, so the run counts the units being off, not coal being unused.

How it is worked out

The history job boils each month down to a short summary when the month is built: for each half-hour record, every half-hour that beat everything earlier in the month (a record must be one of those, so joining the months in order gives every record and its progression); each month’s figures; and the runs at the month’s start and end and the longest inside it. It then publishes the records whenever the history is complete, with the time and a day’s worth of context for each half-hour record (that day’s series, demand, prices, HVDC and the biggest wind or solar farms).

Code: ingest/records.py (the records), site/src/lib/records/records.js (names, wording and the live check).

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