Less than one year ago the national average price for regular gasoline was $2.96 per gallon, and many consumers simply wrote off monthly fuels costs as a mere annoyance.

Those days are over, according to a study released today by Edmunds.com.

Edmunds.com data show that with gas prices at $4.06 per gallon (the average national price for regular fuel on July 21), there are 60 vehicles in the new-vehicle market that cost consumers more than $100 to fill.

In a separate analysis, Edmunds.com has also calculated that the median household is spending 11.5 percent of its income on gasoline expenses, up from 4.6 percent five years ago.

“Gas prices are rising much faster than household incomes,” said Jesse Toprak, Executive Director of Industry Analysis, Edmunds.com. “The result is a difficult situation in which consumers must alter their driving habits or make other sacrifices in their lives.”

A specific example is as follows: A family owns a fuel-thirsty 2008 Nissan Titan XE 4dr Crew Cab 4WD LB (14.3 mpg) and a relatively efficient 2005 Chevrolet Impala Base (22 mpg). If each vehicle is driven 15,000 miles per year, a household with the median income for 2008 will spend $587 per month on gasoline, or 14.6 percent of its income. Of course, most consumers react to individual gas receipts. And in the case of the Titan, consumers are reminded of this major expense every time they go to the pump, as the truck’s 37 gallon fuel tank costs $150 to fill.

“The $100 gas tank is a daunting psychological barrier for many consumers,” said Philip Reed, Senior Consumer Advice Editor for Edmunds.com. “Even drivers who need their big trucks and SUVs may start to reconsider their purchase decision once the gas pump reaches that horrifying $100 number.”