Generation Mix
Where New Zealand's electricity comes from — the plants, the sources, and why the mix matters.
The 2024 Mix at a Glance
New Zealand generated 43,879 GWh in 2024 — enough to power about 5 million average homes for a year. Here's where it came from:
📊 Annual average electricity generation — actual mix varies materially by season, hydrology, and demand conditions. During dry years or winter peaks, thermal generation share increases significantly.
💧 Hydro
🌋 Geothermal
💨 Wind
🔥 Thermal (Gas + Coal)
Dry conditions cut hydro output to the lowest since 2013. Coal generation doubled to fill the gap. Yet renewables still hit 85.5% — down from 88% but still among the world's highest. The new geothermal and wind plants that came online were critical.
Hydro: The Backbone
Hydropower has been central to New Zealand's electricity system since the early 1900s. With over 100 plants spread across both islands, hydro typically provides 55-60% of generation — but that share swings significantly based on rainfall.
The South Island holds most of the capacity, feeding demand in the North via the HVDC link. The major schemes are engineering marvels: Manapōuri's machine hall sits 200m underground, and Benmore created the largest artificial lake in Australasia.
| Power Station | Capacity | Commissioned | Location |
|---|---|---|---|
| Manapōuri Meridian | 800 MW | 1971 | Fiordland (South) |
| Benmore Meridian | 540 MW | 1965 | Waitaki (South) |
| Clyde Contact | 432 MW | 1992 | Clutha (South) |
| Maraetai Mercury | 360 MW | 1952 | Waikato (North) |
| Roxburgh Contact | 320 MW | 1956 | Clutha (South) |
| Ōhau A, B, C Meridian | 264 MW total | 1977-84 | Waitaki (South) |
NZ's hydro lakes hold about 3,600 GWh — roughly 5 weeks of national demand. That's shallow compared to Norway or Canada. Dry periods quickly deplete storage, forcing reliance on thermal backup and causing price spikes.
No new large hydro since 1992. Environmental opposition, high costs, and limited remaining sites mean hydro capacity has plateaued. Future growth comes from wind, solar, and geothermal.
Geothermal: The Baseload Workhorse
New Zealand sits on the Pacific Ring of Fire, giving it exceptional geothermal resources — particularly in the Taupō Volcanic Zone. Unlike hydro, geothermal runs 24/7 regardless of weather, providing critical baseload generation.
Wairakei (1958) was the world's second large-scale geothermal plant. Since then, NZ has built 17 plants across 8 geothermal fields. Capacity hit ~1,300 MW in 2024 after Tauhara came online — a 21% jump.
| Power Station | Capacity | Status | Field |
|---|---|---|---|
| Tauhara Contact | 174 MW | New 2024 | Tauhara |
| Te Mihi Contact | 166 MW | Operating | Wairakei |
| Nga Awa Purua Mercury/Trust | 140 MW | Operating | Rotokawa |
| Wairakei Contact | 132 MW | Retiring ~2027 | Wairakei |
| Kawerau Mercury | 100 MW | Operating | Kawerau |
| Ngatamariki Mercury | 82 MW | Operating | Ngatamariki |
The Geothermal Strategy aims to double geothermal capacity. In 2024, NZ added 225 MW — over half of global geothermal additions that year. Tauhara features the world's largest single-shaft geothermal turbine (184 MW rated).
The catch: Geothermal isn't zero-emissions. CO₂ dissolved in geothermal fluids is released during generation. NZ plants average 115-130 g CO₂/kWh — better than gas (~400g) but not zero. Modern plants like Tauhara reinject CO₂ underground.
Wind: The Growth Story
New Zealand lies in the path of the Roaring Forties — among the world's strongest and most consistent winds. Yet wind generation only reached ~9% in 2024. That's changing fast: capacity nearly doubled from 691 MW (2020) to 1,269 MW (2024).
Most wind farms are in the lower North Island (Manawatū/Wairarapa), taking advantage of wind funneling through the ranges. The South Island has excellent wind but fewer farms due to transmission constraints.
| Wind Farm | Capacity | Commissioned | Region |
|---|---|---|---|
| Turitea Mercury | 222 MW | 2023 | Manawatū (NI) |
| Harapaki Meridian | 176 MW | 2024 | Hawke's Bay (NI) |
| Tararua I-III Mercury | 161 MW | 1999-2007 | Manawatū (NI) |
| Waipipi Mercury | 133 MW | 2021 | Taranaki (NI) |
| Te Apiti Meridian | 91 MW | 2004 | Manawatū (NI) |
| West Wind Meridian | 143 MW | 2009 | Wellington (NI) |
2,000+ MW consented but not yet built. At current build rates (~150-180 MW/year), wind could hit 20% of generation by 2030. Key projects: Puketoi (228 MW), Kaiwera Downs Stage 2 (155 MW), Mahinerangi Stage 2 (164 MW).
Solar: Late to the Party
Solar provides just 1.4% of NZ generation — tiny compared to Australia (25%+). Why? Hydro and geothermal were already cheap and plentiful. But that's changing as solar costs plummet and new farms come online.
Total capacity hit ~450 MW in 2024, up 51% from 2023. Most is distributed rooftop solar (349 MW), with utility-scale farms growing rapidly. New farms like Kohirā, Naumai, and Rangitaiki added 87 MW in 2023-24.
Near Ashburton in Canterbury. Only became NZ's largest in late 2024 — showing how nascent utility-scale solar is. For comparison, Australia's largest is Murray River (640 MW).
The opportunity: NZ has abundant land with good irradiance, especially in Canterbury, Marlborough, and Hawke's Bay. Expect rapid growth as costs fall and demand rises from electrification.
Thermal: The Controversial Backup
Gas and coal provided 14% of generation in 2024 — up from 12% the year before due to low hydro. These plants are emissions-intensive and increasingly expensive, but remain critical for security of supply.
| Power Station | Capacity | Fuel | Role |
|---|---|---|---|
| Huntly Genesis | 1,435 MW | Coal/Gas | Dry-year backup, baseload |
| Stratford Contact | 585 MW | Gas | Peaking, backup |
| Whirinaki Contact | 155 MW | Diesel | Emergency reserve |
Huntly is NZ's largest power station and its biggest source of electricity emissions. Genesis has mothballed some units but keeps Rankine 2 available for dry years. The other three gentailers now pay Genesis to maintain it as "strategic reserve." Without it, 2024's dry spell could have meant blackouts.
The transition challenge: As renewables grow and demand electrifies, the system needs flexible backup that can ramp fast. Gas plants can do this; replacing them with batteries or pumped hydro is the next decade's puzzle.
The Dry Year Problem
New Zealand's reliance on hydro creates a unique vulnerability: dry year risk. When rainfall is low, hydro lakes deplete, prices spike, and thermal plants run hard. It's the defining challenge of NZ's electricity system.
2024 was a test case. May-July saw the driest conditions in decades. Hydro output fell 11%. Coal generation more than doubled. The aluminium smelter at Tiwai Point was asked to reduce consumption by 185+ MW to free up power. Wholesale prices spiked above $200/MWh.
A pumped hydro scheme at Lake Onslow in Otago could store 5,000 GWh — enough for 3-4 months of national demand. Cost: $15-20 billion. Status: Under investigation but no commitment. It would eliminate dry year risk but the price tag is daunting.
Other mitigations:
- More geothermal (runs regardless of rain)
- More wind (different variability profile to hydro)
- Grid-scale batteries (short-term firming)
- Demand response agreements (like Tiwai Point)
- HVDC upgrades (better North-South flow)
💡 The Big Picture
NZ's generation mix is among the world's cleanest — but it's also uniquely weather-dependent. The path to 100% renewable requires solving dry year risk without Huntly, scaling wind and solar dramatically, and managing a system where half the generation varies with rainfall. The pieces are in place; execution is the challenge.