Lise Miller already has picked out the license plate for her recently purchased Honda Civic Hybrid: "SVS GAS."

Miller, a home healthcare worker in Kahulu'u, is part of a growing rank of drivers trading in gasoline-chugging vehicles in favor of miserly gas-electric hybrid vehicles. Three weeks ago she bought a used 2003 Civic Hybrid, which gets as much as 46 miles to the gallon, and sold her Mazda van, which got about 18 miles to the gallon.

"This is really going to help out," said Miller, who drove the silver-blue sedan 510 miles on one fill-up. "It's clearly saving me a lot."

Hybrid vehicles represent a small but growing segment of the auto market as more models become available, performance improves and gasoline prices surge. In Honolulu, regular gasoline prices have spiked 55 cents a gallon in the last month to $3.137 a gallon, according to the AAA Daily Fuel Gauge Report.

That's making more people take an interest in hybrids, which already were a hot seller, as well as smaller fuel-efficient conventional cars, said Morrie Stoebner, president of Honda Windward in Kane'ohe.

"We're sold out of all the hybrids," he said. "We're almost sold out of all our economy cars."

High gasoline prices aren't forcing drivers to shed their sport utility vehicles en masse. However, there are signs that interest in some larger vehicles may be waning.

As of August, the average trade-in value for a large, three-year-old SUV was $17,571 — down 9.3 percent from the average trade-in value in August 2004, according to online information guide Edmunds.com. The trade-in value for a three-year-old midsize SUV was $13,928, up 10.4 percent from August 2004.

Dealers are offering larger incentives to move some SUV models off the lot, said Alex Rosten, an Edmunds market analyst.

"The demand has been slowing for a while, but once gasoline hit $3 a gallon, we've seen a shift," he said. "It doesn't mean people aren't buying SUVs. Instead of buying a large SUV, they may buy a midsized one.

"If you wanted a large SUV, it's a great time to get it."

The shift away from SUVs isn't uniform. For example, sales of luxury SUVs continue to do well, as do sales of midsize SUVs, said Mike McKenna, owner of Windward Ford.

At the same time the hulking Ford Excursion SUV, which once generated four to five sales a month, is garnering less interest.

"If we sell one a month, we're lucky," McKenna said. "That's a big, heavy car. We're seeing more of the bigger cars being traded in and people going to smaller cars, but not that many."

And hybrids are flying off the lot. "Every one we get, we sell," McKenna said, referring to Ford's Escape hybrid.

Before you run out to buy a hybrid, it makes sense to pencil out what the savings would actually be. While more fuel-efficient, hybrids don't necessarily save you money.

For starters, hybrids typically sell at a premium over non-hybrid vehicles. Because of the additional engine components, hybrids fetch a slight premium to their traditional counterparts and typically aren't discounted by dealers. That difference is partly offset by a $2,000 federal tax deduction for those purchasing a hybrid this year. That translates into about a $560 saving for someone in the 28 percent tax bracket.

The 2004 Honda Civic Hybrid, for example, has a starting price of $19,900, which is about a $2,540 premium over its nonhybrid counterpart. Recouping that added cost could take the typical driver about seven years at today's gasoline prices. Of course, the higher gas prices rise, the quicker the hybrid will pay for itself, Stoebner said.

"It definitely makes more sense now" with gasoline prices rising, he said.

For some hybrid buyers, purchasing a fuel-efficient car isn't just about saving money, but saving the environment by burning less oil.

"It's definitely the right thing to do," Joe Ferraro, a Honolulu architect who bought a dark-gray Toyota Prius hybrid car about nine months ago. "I knew that prices would get higher, and I know our supply of oil is diminishing.

"At work I'm interested in sustainability. I figured I'd practice what I preach."

Hybrids work by combining a gasoline-powered engine with an electric motor. The electric motor runs the car when it is charged; the gas engine takes over when needed. Electric power is provided by batteries that automatically charge when the brakes are applied. They don't need to be plugged into an external charger.

Locally, sales of hybrids are gaining momentum. Through June there were 244 new Toyota Prius cars registered in Hawai'i, which was up 33 percent from a year ago, according the Hawaii Automobile Dealers Association. Nationwide, sales of hybrids are expected to rise from 0.5 percent of the new vehicle market last year to 11 percent of sales by 2012, according to J.D. Power and Associates.

Servco Automotive, which runs the Toyota dealerships in Hawai'i, said there's a two-month waiting list for the $21,815 Prius, which advertises mileage of 55 miles per gallon.

"It's only limited by our allocation from the factory," said Wes Kimura, a vice president at Servco Automotive. "If we had more, we don't know what the top side would be."

Reach Sean Hao at shao@honoluluadvertiser.com.