Reservoir Watch
New Zealand runs on hydro, so storage is reported as energy (GWh). There is no official national “percent full”, so levels are shown against the 93-year average and the 1927–2025 range.
Energy stored
3,400 GWh
vs 93-yr average
128%
In historical range
56%
Tracked lakes
3
Storage is energy, measured against normal — not “% full”. New Zealand’s grid is largely hydro, so reservoir storage is reported in GWh. No agency publishes an official national filling degree (percent full), so there is no honest “100%” to divide by. Levels are therefore shown as energy stored versus the 93-year average and the 1927–2025 range. Figures are read from Meridian/NZX’s weekly Comparative Hydro Storage chart and are approximate.
New Zealand at a glance
National storage
3,400 GWh
Above average · 28% above average
min (1927–2025)2,650 GWh
93-yr avg4,700 GWh
max (1927–2025)
vs 93-yr average
128%
Position in 1927–2025 range
56%
Tracked
2 islands · 3 lakes
Source: Meridian/NZX Comparative Hydro Storage (weekly, energy basis, excludes contingent storage). Last reading: 2026-07-27. Figures are read from the weekly chart and are approximate.
By island
Most storage is in the South IslandBy lake
Largest controllable storagesAbout New Zealand’s hydro storage
New Zealand generates most of its electricity from hydropower, and almost all of its controllable storage sits in a handful of large South Island lakes — Pūkaki and Tekapo on the Waitaki, Te Anau and Manapōuri in the south, Hāwea on the Clutha — plus Lake Taupō in the North Island. Because that storage is drawn on to keep the lights on, it is measured as energy (GWh), not water volume.
There is no official national filling degree (percent full), so the meaningful question is not “how full” but “how does storage compare with normal for the time of year”. As of 2026-07-27, national storage was 28% above average — above average. Storage is typically drawn down through winter and refills with spring inflows; comparing the current figure with the 93-year average and the historical range shows whether the country is running wet or dry.
Frequently asked questions
How full are New Zealand’s hydro lakes right now?
As of 2026-07-27, national hydro storage was about 3,400 GWh — 28% above average (above average) for late July, and roughly 55.9% of the way up the 1927–2025 range. New Zealand does not publish an official national “percent full”, so storage is compared against the historical average instead.
Why is New Zealand shown in GWh and “% of average”, not “% full”?
New Zealand’s grid is largely hydro, so storage is reported as the electricity it can generate (GWh). Unlike Norway or Colombia, no agency publishes an official national reservoir filling degree (percent full), so there is no honest “100% full” to divide by. The standard, sourced way to read New Zealand storage is therefore energy stored versus the 93-year average and the 1927–2025 range — which is what these pages show.
Which lakes and regions are tracked?
Three tracked lakes — Lake Pūkaki (Waitaki scheme) and Lakes Te Anau and Manapōuri (Manapōuri/Waiau scheme), New Zealand’s largest controllable hydro storages — plus South Island and North Island totals and a national figure. Almost all of New Zealand’s controllable hydro storage sits in the South Island.
How current and precise is the data?
The figures come from Meridian/NZX’s weekly “Comparative Hydro Storage” report, which is published as charts rather than a data table, so values are read off those charts and are approximate. They are updated weekly.