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 that supports Tasmanians' ambitions.

Secure energy

In 2017 (as an example of a fairly typical year), Tasmania’s energy generation mix was:

Hydropower generation 70% (about 8200 GWh)
Wind generation 10% (about 1000 GWh)
Gas generation 8% (about 900 GWh)
Basslink imports from mainland 12% (about 1400 GWh)

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.

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.

We aim to have storages at 30 per cent or more on 30 June each year (going into what’s generally the wettest period), and 40 per cent or more at the start of summer (1 December) - As of Monday 27 November, Hydro Tasmania storages were at 44.9%. The business will comfortably exceed its operating target of 40% at the start of summer (1 December) - targets which are higher than the approved PSL for those dates.

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.

You can now monitor Tasmania’s energy security for yourself, by comparing the storage figure to the High Reliability Level (HRL) and Prudent Storage Level (PSL).

The Tasmanian Economic Regulator (TER) also releases an Annual Energy Security Review every November, along with monthly dashboard updates, assessing Tasmania’s energy security at a point in time.

The first TER Annual Review was released on 29 November 2017, and is available on the TER website.

Secure energy infographic
© Hydro-Electric Corporation 2018