Flick a light switch, plug in a computer or turn on the TV . . . the result is instantaneous. We don't think about where it is coming from or how efficiently it is being produced. But, based on the latest information about the worrying number of amber alerts in the Irish electricity system, perhaps it's time we started to.

It is important to state at the outset that nobody is talking about a repeat of the 1998 Auckland power crisis . . . when the city's central business district suffered a five-week power outage . . .

happening in Ireland.

However, there is cause for concern about the tightening margin between capacity and demand for electricity. And there is a growing view that, unless action is taken to address this problem, power outages may, within two or three years, become an undesirable feature of the Irish economy.

The basic problem is that, since the birth of the Celtic Tiger, electricity consumption has increased at a rate that has mirrored the dynamic growth in the economy. Against that, while a number of new electricity generation plants have, or are due to, come on stream, the rate of supply growth has not matched soaring demand.

For obvious reasons, demand is higher in winter, and on 13 December last, a new record was set when demand levels reached 4,823 megawatts. Just to put that into context, three years ago, there was only 5,100MW of power in the entire electricity grid.

Today, because of some new plants, the hiring of emergency generators and the interconnector with Northern Ireland, the capacity is around 6,000MW.

That might seem like a comfortable margin, but it does not tell the full story. In an answer to a Dail question recently, natural resources minister Noel Dempsey said the "availability performance of some of the existing older ESB generation plant is giving cause for concern and has been for some years".

While performance had improved in 2004 and in the first half of 2005, it "declined again in the second half of last year as a result of the breakdown of several large ESB generation units".

Unconfirmed reports suggest that, at times, up to 25% of this capacity has been unavailable . . . the industry norm is around 10%. It is understood that the latest figures from the ESB national grid show a typical plant availability rate of around 82%. That indicates that, at any given time, around 5,000 megawatts of power is available . . . suggesting a tight margin for error on days when demand is high.

Dempsey confirmed in his Dail answer that the "margin between capacity and demand for electricity is tighter than normal this winter".

Last year, there were 57 so-called 'amber alerts' in the electricity system, along with one red alert. The reasons for the red alert on 5 August last . . . when there was a temporary loss of supply to 326,000 customers . . . are complex, and the minister assured the Dail that the combination of factors is "unlikely" to recur.

Of more concern, however, is the number of amber alerts, issued at the point when a single event, such as the outage of a power plant, would give rise "to a reasonable possibility of failure to meet demand for electricity". The sharply increased number of such alerts hardly gives grounds for confidence. Nor does the widespread belief in the industry that special mobile generators brought in to provide emergency back-up are being used almost daily to supplement a creaking generating system.

The good news . . . and the reason there appears to be no short-term danger of black-outs . . . is that two new plants are due to be completed shortly. Tynagh in Galway and Aughinish Alumina will bring another 500 megawatts of capacity to the grid, while the construction of a second plant at Huntstown in north Dublin will also bring an additional 400 megawatts by the end of 2007.

The bad news, say Green Party TDs Eamon Ryan and Trevor Sargent, is that after those three plants, there is nothing on the horizon.

The Greens say Ireland's market is caught in a postderegulation 'Catch 22'.

Because of ESB's dominant position that allows it to set the market price, the Irish market is not attractive to private investors. However, that very dominant position means the regulator is unlikely to allow ESB to build any new generating plant or invest significantly in its existing plant, even though it can spend millions doing so in the North or in Spain.

Eamon Ryan believes that, by 2008 or 2009, there is a "very real possibility" of blackouts unless immediate action is taken to add new capacity into the system.

He is not alone. One union source said nobody close to the energy sector would deny that there is a fear of future blackouts. "If emergency generators are being used all the time, that says it all, " he said.

One doesn't need to be an economist to realise the damage blackouts would do to the economy and, in particular, foreign investment. However, there is little sign that the issues are going to be addressed in the near future.

Consultants Deloitte have completed a report on the electricity sector. However, minister Dempsey . . . not unreasonably . . . wants to wait for a white paper on the future of energy policy to be completed later this year before releasing the report.

Rightly or wrongly, the suspicion is that the Deloitte report will recommend selling some of ESB's plants or breaking up the company into smaller competing entities. Clearly, there is no way that will wash with the ESB unions, which have already succeeded in watering down the plan to separate the management of the national grid from ESB.

And the fear in industry and political circles is that, given the taoiseach's legendary closeness to the unions, such thorny issues will not be grasped until after next year's general election at the earliest. That would leave little time to tackle potential electricity demand shortfalls in 2008/09, leaving, as Ryan notes, the "Irish economy in a very vulnerable position".

As things stand, nobody is happy. Both the ESB unions and the private sector believe the market is skewed against them. At the moment the public is blissfully unaware of any potential problems, but that would change overnight if predictions of supply shortfalls in two or three years' time prove accurate.

Throw in longer-term concerns in some quarters about an overdependence on gas from eastern Europe and it all adds up to a massive headache for the government.

Noel Dempsey has a reputation for being one of the more innovative and original thinkers in the cabinet. It's going to take all his skills to sort out this conundrum. And the stakes simply could not be higher.