Tasmania's hydro-electric scheme has long seen the island state finish first in Australia's renewable energy race.

But what happens when the water starts to run out?

That’s the awkward predicament that has left Tassie’s Liberal administration praying for rain after a particularly dry and mild summer.

And it’s been compounded by an ill-timed breakdown of the Bass Strait electricity cable, leaving the apple isle isolated and sparking fears the lights could go out.

In an affront to the state’s strong environmental movement, a quick-fix solution has come in the form of diesel generators, costing more than $40 million to hire and install, with ongoing monthly operating costs of about $11 million.

“I know people don’t like it, I know it’s expensive, but we’ve got no choice,” Energy Minister Matthew Groom told parliament of his backup plan.

Water levels in hydro dams have dipped to just 14.8 per cent and continue to fall faster than forecast.

“It will rain, it will rain in this state, the history of Tasmania proves that is the case,” Mr Groom said.

However, the Bureau of Meteorology isn’t forecasting any significant rainfall during coming months.

Deals have been struck with some major industrial energy users to rein in their drain on the grid and in the meantime the ring-in generators are firing and the Tamar Valley natural gas-fired power station is working hard.

But Labor Opposition Leader Bryan Green is one of many cynics of plan B.

He told the lower house on Tuesday the state is just 12 weeks away from producing its last drop of hydro energy, and thereafter demand for power will outweigh supply.

“It’s an extremely dangerous strategy,” Mr Green said.

“(The minister) is blindly leading Tasmanians through the worst energy crisis in the state’s history.”

The Greens are similarly scathing.

“You’re drunk on diesel,” party leader Cassy O’Connor told Mr Groom.

Meanwhile, some 90km off shore from George Town in Tasmania’s north, operators Basslink have cut their high-voltage cable which lies on the seabed and stretches to Victoria.

An unknown problem saw the direct current supply go offline in December, leaving Basslink to undertake a tedious search for the trouble spot.

It couldn’t have come at a worse time, amid trying conditions and high demand for electricity, Tasmania was relying on the cable for more than a third of its energy needs.

A replacement section of cable is on its way from Melbourne, but conservative estimates – weather permitting – have the cable back online some time in May.

Until then, or at least until it rains, the government seems destined to come under attack for failing to have insured against such a situation.

“I can’t predict the future, just as I can’t control the rain, I can’t control the timing of Basslink,” Mr Groom said.

“What I can say is that we have an energy security plan in place to maintain the energy requirements of this state.”

The minister warned that dam levels will go lower before they improve, and said expert advice suggests hydro-electric generation will not be possible once water levels reach 6.5 per cent.

“What is the contingency if we get to a stage where you can’t draw on water? Or is your plan to just keep hoping it will rain?” Mr Green asked.

“You know there is not enough generating capacity from the Tamar Valley power station and your diesel generators to power Tasmania’s economy and to keep Tasmanians out of the dark.”

Mr Groom said his two-phase plan firstly accounted for an extended Basslink outage until the arrival of winter rains. If necessary a subsequent tranche will see see additional gas-powered energy generation.

“The government continues to encourage Tasmanians to be prudent and sensible with their electricity usage, particularly as we start to experience cooler nights and mornings,” he added.

Adding to the woe, the Bass Strait cable failure also knocked out regular internet connections which use the seabed fibre optics.

Service provider TPG failed to heed warnings given months in advance that ISPs would need to negotiate additional capacity on Telstra cables while Basslink repairs were carried out, the government said.

Therefore some users lost connectivity until extra bandwidth could be negotiated.

The government has called on the Australian Competition and Consumer Commission to ensure pricing sticks to regulated levels, as there is a joint use of cables.