Hawaiian Electric Co. could have prevented Sunday's blackout on O'ahu but only by building redundant systems that would jack up electric bills, according to consumer advocates, utility experts and earthquake engineers.

You can pay hundreds of millions of dollars for a system that never shuts down, or you can tolerate a blackout once every 15 to 30 years, the experts said.

"Do you really want to gold-plate your system for something that may occur once every 30 years?" asked Mindy Spatt, communications director for The Utility Reform Network, a San Francisco-based consumer group that represents utility customers in California.

Once you build it, "the only thing you can be sure of is that the cost will be passed to consumers," Spatt added.

It would cost more than $1 billion to construct a parallel or redundant system that would have allowed HECO to continue providing service after a big earthquake, said Clark Gellings, vice president of innovations with the Electric Power Research Institute in Palo Alto, Calif.

That works out to an average $3,400 per HECO customer.

"Power systems aren't designed to be completely foolproof. If we did design them that way, you or I couldn't afford electricity," said Gellings, whose organization provides research for the nation's electric power industry.

Sunday's failure, which left 291,000 HECO customers without electricity for most of the day, was triggered by a 6.7-magnitude earthquake off the coast of the Big Island. Gellings said most power systems in the country would have suffered outages if a 6.0-magnitude or greater earthquake were to hit within the area.

CALIFORNIA QUAKES

The 7.1-magnitude quake that hit the San Francisco Bay Area in 1989 and the 6.7-magnitude Northridge earthquake in 1994 interrupted electrical service to thousands of customers, Gellings said.

"If there's an earthquake, there will be interruptions," added Jim Feltes, senior manager of Siemens Power Transmission & Distribution Inc., a consulting company that runs electrical power systems analyses.

"There are certain design standards that apply to equipment in terms of earthquakes ... but when everything shakes around, at the minimum you are going to get small outages," Feltes said.

A backup system to prevent outages during earthquakes would have to be located in an area that wouldn't be affected by an earthquake, Gellings said. The utility also would have to build extra transmission lines, which would add to the cost.

"There's only one place the utility could go to recover that expense, and that is the consumer," Gellings said.

John Clinton, co-founder of Richmond, Calif., architecture and engineering firm Interactive Resources, said utilities can take some steps to mitigate earthquake damage by adding extra bolts to generators and metal braces or more sophisticated machinery to dampen the shaking during a quake.

But Clinton, whose firm conducts work for Pacific Gas & Electric Co. in California and managed the seismic upgrades for San Francisco's Candlestick Park before and after the 1989 earthquake, said that outages can occur even with the seismic upgrades if a power system's transmission lines are exposed.

CHAIN OF EVENTS

Sunday was the first islandwide blackout since 1991, when a fallen tree took out a power line that led to a rolling shutdown of all generators.

Sunday's initial quake, which was followed minutes later by a 6.0 temblor, tripped off three HECO generators, or roughly 25 percent of the utility's peak capacity. The downed generators in turn set off a chain of events that led to the automatic shutdown of electricity on O'ahu.

HECO spokesman Jose Dizon said the company's power system has been able to withstand earthquakes in the past, but Sunday's 6.7-magnitude quake was the largest in some time.

"I guess you can bulletproof your system, but at what cost?" Dizon asked.

HECO has begun an internal investigation into the blackout and will present some of its preliminary findings to the state Public Utilities Commission during a briefing this afternoon.

HECO officials wouldn't say whether any of its power plants on O'ahu have been retrofitted for earthquakes. They would only say that the plants and generators are built under a more stringent standard than the current standard for commercial buildings.

Reach Rick Daysog at rdaysog@honoluluadvertiser.com.