Tasmania generally consumes about 10,600 gigawatt hours of electricity each year. Meeting that demand and giving Tasmanians a secure and reliable energy supply is Hydro Tasmania’s absolute highest priority. We’re proud to do so in a clean and renewable way.

Secure energy

The total aggregate amount of water in our storages is known as Total Energy in Storage (TEIS). It’s the headline storage figure you often hear and see in the media.

TEIS hardly ever goes above 50 per cent or below about 25 per cent. It generally peaks in the 40s during the wettest part of winter and spring each year, and bottoms out in the 20s in the driest part of autumn and summer. Both levels are normal and secure. They just represent different extremes in the seasonal cycle.

Tasmania's energy security is measured by comparing the storage figure against the High Reliability Level (HRL). As the name suggests, this figure represents a level where we have high reliability of energy supply - at this level, even with very dry weather AND a six month Basslink outage, we would still have enough energy in storage to meet Tasmania's needs.

Secure energy infographic

The Tasmanian Economic Regulator (TER) releases an Annual Energy Security Review every November, along with monthly dashboard updates, assessing Tasmania's energy security at a point in time. These reports are available on the TER website.

Because more than two-thirds of Tasmania’s energy comes from hydropower generated right here in Tasmania, there’s often great interest in our water storage levels, and how we manage them.

So why doesn’t TEIS ever really go above 50 per cent?

A 100 per cent storage level reflects the absolute maximum amount of water that a lake or lagoon can actually hold. But in reality, the water never gets anywhere near that level. Nor should it.

At 100 per cent full, the lake would be much larger than its ‘normal’ size and appearance. Boat ramps and fishing spots would be underwater, and you’d face the possibility of flooding with just a sprinkle of rain or a puff of wind.

Just as you don’t fill a bath to the very top, lakes aren’t meant to be anywhere near totally full. Indeed, non-hydropower catchments are naturally kept in check by rivers and evaporation taking water away.

Natural factors aside, building up storages to very high levels would be extremely inefficient and uncommercial. That huge amount of unused water would represent a huge amount of clean hydropower that we’d failed to generate.