Who doesn’t like to save a buck?

A little extra cash is especially nice in this age of stagnant incomes. So a sharp decline in the price of gasoline is a holiday gift, made even sweeter by projections that fuel costs will stay down well into 2015.

After peaking at $3.70 a gallon in April, the national average has fallen by more than a dollar, ending the week at $2.45 — the lowest price in five years. Here in Santa Rosa, gas could be found for as little as $2.43 a gallon.

Those pennies at the pump add up to substantial savings.

If gas prices stay low, Mark Zandi, the chief economist at Moody’s Analytics, estimates that American consumers could gain $100 billion in disposable income over the next year. “It could make the difference between a good year and a great year,” Zandi told the Los Angeles Times.

Gas prices are falling because of a worldwide decline in the price of oil — the result of an economic slowdown in Europe, an increase in North American production and the OPEC cartel’s decision to maintain current production levels.

The windfall for consumers is accompanied by economic pressure on oil-dependent states such as Russia and Iran. Declining prices also are a problem for the Islamist rebels of ISIS, who finance their military ventures in Syria and Iraq by selling oil.

Enjoy it while it lasts, but it’s foolish to imagine that oil prices will stay low forever.

So before they start rising again, let’s think about the abysmal condition of California’s streets and highways. More to the point, are we willing to spend some of the windfall on better roads?

And if so, is it time for a new funding source?

Gas taxes are the primary source of money for road maintenance and rehabilitation. But sales of gasoline have been declining for nearly a decade as car buyers opted for more fuel-efficient vehicles and, until the recent drop in gas prices, motorists traveled fewer miles. Inflation, meanwhile, drives up the cost of construction while pushing down the buying power of gas tax revenue.

All of that contributed to a multi-billion dollar shortfall in the state’s road maintenance fund. California isn’t unique. Without an $11 billion infusion from other revenue sources, the federal highway trust fund would have been exhausted and repair projects would have been halted at the height of the summer construction season.

In 2015, Oregon will test an alternative — a tax based on miles driven instead of fuel purchased.

Drivers will be charged 1.5 cents per mile, with a variety of means — GPS, odometer devices and daily diaries — used to track miles.

California, which recently allowed insurers to base premiums on mileage, is considering its own test of a mileage tax.

A mileage-based tax could benefit Sonoma County, which is badly shortchanged by a state formula for distributing gasoline taxes that favors larger counties, even if they have fewer road miles.

Let’s talk now — before gas prices rise and, as always, the hunt begins for a political scapegoat.