Understanding NZ Fuel Supply
A plain-language guide to how New Zealand's fuel system works and what the numbers on this dashboard mean.
What are "days cover"?
Days cover is the most important number on this dashboard. It tells you how many days New Zealand's current fuel stocks would last if no new supply arrived. A days cover figure of 30 means that at current consumption rates, the country has 30 days of fuel in reserve.
Days cover is calculated by dividing total stock volume (measured in megalitres or tonnes) by average daily consumption. MBIE publishes this figure weekly for petrol, diesel, and jet fuel separately.
New Zealand typically maintains between 20 and 60 days cover depending on the fuel type and season. The key reference points on this dashboard are the current MSO thresholds: 28 days for petrol, 21 for diesel, and 24 for jet fuel.
What is the MSO?
The Minimum Stockholding Obligation (MSO) is a legal requirement set by the New Zealand government under the Fuel Industry Act 2020. It requires fuel importers and wholesalers to hold a minimum volume of fuel onshore, or on ships in New Zealand's EEZ, depending on the compliance rules that apply to them.
The current MSO thresholds are:
- Petrol: 28 days of in-country stock
- Diesel: 21 days of in-country stock
- Jet fuel: 24 days of in-country stock
The "in-country" qualifier is important for our dashboard, but it is not the full legal definition. On-water stocks outside New Zealand's EEZ do not count toward the MSO. When compliant stock falls below the MSO, the government can require importers to increase their holdings or face penalties.
In-country vs on-water stocks
Total days cover includes both in-country stocks (fuel already at New Zealand terminals, storage sites, and other onshore facilities) and on-water stocks (fuel currently in transit on tankers heading to NZ ports). On-water stocks can represent a significant portion of total cover, sometimes 10 to 20 days worth.
This distinction matters because on-water fuel is not yet available for use. A scenario where total cover looks adequate but in-country cover is below MSO thresholds is a genuine supply risk — a storm, port closure, or vessel delay could quickly create a shortfall.
This dashboard shows both figures. The AI risk assessment specifically focuses on in-country cover relative to MSO, rather than the headline total, because it is the more meaningful indicator of near-term risk.
Where does New Zealand's fuel come from?
New Zealand closed its only domestic refinery (Marsden Point, Northland) in 2022. Since then, the country imports all of its refined petroleum products — a significant change that increased dependence on international supply chains.
The majority of NZ's fuel is imported from:
- South Korea (~48%): Refineries at Daesan, Yeosu, and Ulsan
- Singapore (~33%): One of the world's largest refining hubs
- Other sources: Japan, Australia, Malaysia
Tankers typically take 10 to 14 days to travel from Korean or Singaporean refineries to New Zealand ports. This transit time means NZ has limited ability to respond quickly to sudden supply disruptions. When refinery capacity is reduced — due to planned maintenance, accidents, or geopolitical events — the impact in NZ is felt 2 to 3 weeks later.
How are tankers tracked?
Commercial vessels are required by law to broadcast their position using the Automatic Identification System (AIS). AIS transponders transmit a vessel's identity, position, speed, heading, and destination every few seconds.
This data is received by coastal stations and satellites, then aggregated by services such as MarineTraffic and VesselFinder. NZ Fuel Watch uses those AIS feeds to track a fleet of known fuel tankers that regularly service New Zealand ports.
In practice, the scheduled-vessels card is best treated as a near-term visibility window, usually strongest for roughly the next 7 to 14 days rather than a complete future shipping forecast. The closer a tanker gets to New Zealand, the easier it is to confirm its route and likely arrival.
AIS data also has limitations. Vessels can turn off their transponders in certain sea areas, satellite AIS coverage has gaps in remote ocean regions, and ETAs reported via AIS are estimates that can change significantly as voyages progress. Different public tracking sites can disagree for a time because they refresh on different schedules, use different receivers, or interpret the same destination signals differently.
That means a vessel mentioned in a news report or another tracker may not appear on NZ Fuel Watch immediately. Sometimes it shows up later as the AIS picture becomes clearer. Sometimes there is still not enough evidence to list it confidently as an NZ-bound fuel arrival.
Why does the Strait of Hormuz matter?
The Strait of Hormuz is a narrow waterway between Iran and Oman through which approximately 20% of the world's oil supply passes. While New Zealand does not import directly from Middle Eastern oil fields, the strait's status affects global crude oil prices and Asian refinery feedstocks.
When Hormuz is disrupted — by conflict, sanctions, or political tension — Asian refineries (including those in South Korea and Singapore that supply NZ) face higher input costs and potential crude shortfalls. This can reduce refined product availability and push up prices for New Zealand importers.
The AI risk assessment on this dashboard includes upstream signals like Hormuz status when evaluating overall supply risk.
What does the AI risk assessment mean?
The AI risk assessment is generated twice daily by analysing current MBIE stock data, upcoming vessel arrivals, pump price trends, crude oil prices, and upstream supply chain news. It produces one of four risk levels:
- Normal: Compliant stock is at or above MSO thresholds with adequate upcoming supply. No near-term concerns.
- Moderate: One or more fuel types is approaching MSO thresholds, or vessel pipeline is thinner than usual. Worth monitoring.
- Elevated: One or more fuel types is at or below its MSO threshold, or the upstream supply chain shows significant disruption risk.
- Critical: Multiple fuel types below MSO with thin incoming supply. Immediate supply concern.
The assessment also includes a trend direction (Improving, Stable, or Worsening) based on four weeks of stock data, a deterministic risk score calculated from stock trajectories and vessel pipeline cadence, and a confidence level reflecting data quality. A 14-day net supply position is calculated for each fuel type — comparing incoming cargo volume against expected consumption over the next two weeks — and fed into the analysis to moderate or escalate the language accordingly.
This analysis is AI-generated and may contain errors. It is not financial or safety advice. Always verify critical decisions with official sources including MBIE and Civil Defence.
How are MSO breach and runout dates calculated?
The Stock Trajectory panel shows two projected dates for each fuel type: the date in-country stock may fall to its MSO threshold, and the date stock could reach zero if no new supply arrives. Neither is a simple trend line — both are produced by a 12-week, week-by-week simulation that accounts for the actual vessel pipeline.
How the simulation works:
- Estimate gross consumption rate. Using historical MBIE data on delivered cargo volumes and observed net stock changes, the model back-calculates how many days of fuel NZ consumes per week for each fuel type (typically 7–12 days/week). When no past MBIE delivery history is available, it falls back to the confirmed upcoming pipeline, then to net stock change alone as a last resort.
- Apply confirmed pipeline data. MBIE publishes a rolling forward view of incoming vessel cargo (in days of cover) each Tuesday. The simulation uses these confirmed figures for the near-term weeks, reflecting the actual thinning or thickening of the pipeline.
- Fall back to historical average. Beyond the MBIE forecast window (typically 2–3 weeks), the model assumes incoming cargo reverts to the historical weekly average. The full simulation runs 12 weeks forward.
- Find the MSO crossing point. The simulation steps forward week by week:
stock(t+1) = stock(t) − consumption + incoming. When stock crosses the MSO threshold, the crossing is interpolated within that week to produce a projected breach date. - Find the runout point. The same simulation continues tracking stock after an MSO breach. If stock reaches zero within the 12-week window, that date is shown as the projected runout date — the point at which a fuel type would theoretically be exhausted.
This approach matters most when the near-term pipeline is unusually thin — for example, when only one vessel is confirmed in the next two weeks versus the normal three to four. In those cases, a simple trend extrapolation would underestimate the risk, while the simulation correctly pulls both dates earlier.
MSO thresholds: Petrol 28 days, Diesel 21 days, Jet Fuel 24 days. Dates shown are estimates based on available data and should be interpreted as trend signals, not precise forecasts. Runout dates assume no new supply — in practice, government intervention or emergency imports would occur well before that point.
What should I do during a fuel shortage?
NZ Fuel Watch monitors supply trends, but is not an official government source. If a genuine fuel emergency is declared, follow guidance from:
General preparedness advice: keep your vehicle tank above half when supply risk is elevated, avoid panic buying (which worsens shortages), and prioritise essential transport needs.