PORTLAND, Ore. — There is one thing that just about everybody agrees has to be done about the thousands of miles of electricity transmission lines that crisscross the West — build more of them.

The big question is, who pays for them? Another is, who controls them? And finally, how much should it cost to use them?

Utility managers and regulators say those questions need to be answered soon — before demand outstrips the power supply to some of the fastest-growing areas of the nation.

Otherwise, the risk of a blackout keeps rising.

The Bonneville Power Administration two years ago completed a transmission system expansion project in the Seattle area, reducing the risk of massive power failures there.

"It reinforced a key link that would have, for sure, put the Seattle area in danger of blackouts had it not been constructed," said Ed Mosey, spokesman for the Portland-based federal power marketing agency.

In Arizona, the largest utility in the state is proposing a new $3 billion pair of 500,000-volt lines to bring power 600 miles from coal and wind turbine plants in Wyoming. It would also let the Arizona Public Service Co. send excess power from the Southwest to the north.

"Arizona's one of the two fastest-growing areas of the country, along with Nevada," said Jim McDonald, spokesman for Arizona Public Service.

The utility relies on coal, nuclear and natural gas-fired generating plants for electricity to accommodate growth that includes Arizona cities like Gilbert, which topped the U.S. Census Bureau's list of fastest-growing cities with at least 100,000 new people from April 2000 to July 2004.

But all that generating capacity has to have a way to reach new businesses and homes — meaning more high-voltage wires, McDonald said.

"So it's very important to have additional infrastructure in the West because of the way the region is growing," McDonald said. "And there hasn't been a substantial investment in that transmission infrastructure."

On Nov. 17, the Federal Energy Regulatory Commission proposed transmission pricing reforms to promote what commissioners said was long overdue investment in energy infrastructure.

The Energy Policy Act of 2005, which President Bush signed in August, directed FERC to develop incentive-based rates for interstate power transmission.

The reforms adopted on Nov. 17 will implement those incentives and provide regulatory certainty needed to reassure utilities and investors, officials said.

The goal is to increase power-grid reliability and lower costs by reducing transmission congestion between states.

"No one is looking at the lights going out," said U.S. Rep. Peter DeFazio, D-Ore. "But what we're looking at now is how do you make the system work better, and how do you avoid duplicate investment in very expensive transmission lines."Reliability and congestion are issues that have been a struggle for utility managers and regulators across the West for more than a decade, as they have watched transmission line construction fail to keep pace with electricity demand.

"We should have been making plans to build out the transmission system years ago," said David Kvamme, spokesman for PacifiCorp.

The Portland-based utility serves 1.6 million customers in six Western states and must balance regulatory demands in each state with the need for additional transmission capacity.