The state Public Utilities Commission is doing some preliminary fact-finding into the Hawaiian Electric Co. outage, as it does with all disruptions of service.

This inquiry needs to be as comprehensive as possible. The islandwide power shutdown frustrated many customers, especially since the public was "left in the dark," literally as well as figuratively, for so long. O'ahu, at least, was lucky that the repercussions of Sunday's earthquakes were relatively limited.

But island residents almost certainly won't be so lucky next time, and the public needs to make the most of this opportunity to fortify capabilities in the event of a disaster.

That's why the commission should use its authority to open a formal investigation. This quasi-judicial process will provide the commission with a solid basis for deciding what changes or improvements in the utility equipment or operations are really needed and should be mandated.

The last outage to trigger such an inquiry followed an islandwide blackout that occurred April 9, 1991. The investigation led to recommendations aimed at improving the network of transmission lines and to avoid contact between trees and power lines, one of the factors triggering the outage.

It's possible that some equipment improvements could be recommended here, although the initial survey would indicate that the existing system of protective relays succeeded in its top-priority task: preventing catastrophic damage to the utility's turbines.

Whether or not any refinements could have improved HECO's efforts to avert the blackout through a partial shutdown process known as "load shedding" could be examined.

In a story reported by Advertiser staff writer Rick Daysog, experts from other utilities rightly observed that adding full redundancies to the system is enormously expensive and surely impractical. But there could be smaller-scale improvements that, through the investigation process, might be found worthwhile.

Among these might be backup communications links to media and key officials that would help HECO give its customers timely information about its services. As a public utility, HECO owes that much to the public.