New Englanders filling their gas tanks in September 2004 paid an average of $1.87 a gallon; this summer the price was $2.54, and for weeks in the wake of Hurricane Katrina, more than $3. In 2003, home heating oil cost $1.23 a gallon, this September it spiked to $2.61. Natural gas prices are projected to be close to 50 percent higher than last winter.

So what’s New England to do?

First, it can ramp up its push for solar, wind power and biofuels. All have historically required some form of subsidy, but today have begun to look quite competitive. Unless world energy prices start to tumble dramatically, the “renewables” will likely prove to be the inexpensive (and reliable) sources of the future.

But for a far swifter impact on energy prices and fossil fuel consumption, New England (like the Bush administration, in the wake of the recent hurricanes) needs to turn fast and hard toward energy efficiency.

Efficiency is the region’s “nearest big-time opportunity” for dramatic energy savings, says Robert Pratt, director of the Massachusetts Renewable Energy Trust.

So what’s “efficiency”? Isn’t that all the stuff we’ve heard for years about installing sensor-activated lights, buying low-energy bulbs? About limiting the power use of every product from television adapter boxes to commercial icemakers? Or rewriting building codes for higher energy efficiency? Or utility-administered programs that pay for home insulation?

The answer: yes, and consumers and businesses in New England and nationwide have already saved billions of dollars by such measures, even while freeing up energy supplies. But the job’s just started. New, improved appliance standards are constantly being proposed: a broad set of rules was approved in Rhode Island in June, with measures pending in all the other New England states.

The allied, big idea is “green” building – every measure from improved materials and insulation to basic design and siting as ways to reduce energy demand in homes, office buildings, schools and stores. The opportunity is massive: buildings account for two-fifths of America’s overall energy consumption and generate a third of its carbon dioxide emissions. Insisting buildings “go green” can yield huge gains. Even in such “slow growth” states as Massachusetts and Connecticut, there are projected to be spectacular numbers of new homes (25 percent-plus increase) and office space (more than 50 percent) in 2030 compared to 2000.

Lots of standard assumptions do need to be challenged to get there. Consider New England’s electricity demand – it’s rising, inexorably, 1.2 percent a year to 2013, according to ISO New England, the group that oversees electric generation and transmission in the six states.

But contrast that discouraging prospect with the “economically achievable energy efficiency potential” calculated by the nonprofit, Northeast Energy Efficiency Partnerships (a coalition of consumer, environmental and energy efficiency groups).

With smart steps now, the group projects, New England could actually do a turnaround and reach 1.38 percent less demand per year. Natural gas demand could be cut by as much as 25 percent by 2013. Investing in energy efficiency could provide net benefits of up to $23 billion for the region’s economy.

One exciting potential: systems of “distributed generation” – local power plants producing modest amounts of electricity within or close to hospitals, apartment houses, factories or neighborhoods. Often operated with cogeneration techniques to produce both electricity and heat, the energy efficiency of such plants is often double or triple that of typical big regional power plants (which typically lose large chunks of their power traveling long distances on transmission lines).

Distributed generation, we heard, could help especially in areas where the New England power grid is perilously overloaded – a problem now severest in Connecticut from Middletown to the New York line, where local opposition has stymied building of sufficient power lines, but also in areas around Boston, southeast Massachusetts, and Burlington, Vt.

Why couldn’t local generation reduce or- maybe eliminate – need for some new transmission lines?

Another plus of local power plants is that while they often power up with natural gas, they’re ideally suited for several emerging new energy technologies – fuel cells, wind turbines, rooftop solar electric devices, even bioconversion based on cow manure. They protect consumers from major power blackouts and reduce vulnerability to terrorist attacks.

Both drawing power from and able to contribute power to large electric grids, they sound like quintessential New England: “distributed, decentralized and democratic.”