On the surface, it looks like a no-brainer.

O'ahu's demand for electrical power just keeps growing, and the ability of Hawaiian Electric to keep up with that demand is faltering.

The obvious solution: Build a new power plant to add capacity and help avoid the kind of blackout that affected much of the island earlier this month.

That, at any rate, is Hawaiian Electric's proposed solution for the situation. The company has been working on plans for some time and is now in the lengthy process of obtaining Public Utilities Commission approval.

Demonstrating that O'ahu needs more power should be easy. The tough part will be convincing the PUC that the best answer is another fossil-fuel-burning plant.

Critics say the extra capacity could be developed without the need for a new plant. They point to alternative sources of energy, ranging from smaller "distributed" generating sources associated with hotels and other major buildings to wind and solar and even ocean wave energy generators.

They also say that the system could be brought back into better balance by encouraging greater conservation.

All of these points are valid, and to a degree Hawaiian Electric is already moving in that direction. One proposed wind farm was rejected by the community, but another is being considered on the Windward side of the island. The company has well-established programs to encourage solar water heating and is moving ahead on photovoltaic systems.

At the same time, the utility has become a much more active player in encouraging conservation.

But will the net sum of all these efforts add up to the power capacity of the new generating plant? Unlikely, at least not now.

The day will surely come when the combination of alternative generation and sophisticated conservation will match or beat the output of a stand-alone power plant. The issue before the PUC is whether we can afford to wait for that day.

Encouragingly, Hawaiian Electric wants to build a plant that could run on methane, a byproduct of the oil we already refine. In addition, it would be engineered to run on ethanol, should an adequate supply ever become available.

For all these reasons, the tilt at this point appears to favor building the new plant. If the PUC agrees, it would be refreshing if Hawaiian Electric could make the same vow it made in conjunction with its new generating facility on the Big Island: that this will be the last centralized fossil-fuel plant it will ever build.