Raising five grandchildren on a salary that never reached more than $13,000 a year, my grandmother, Big Mama, understood the economics of energy conservation.

We never had a clothes dryer. Big Mama didn’t want to increase her electric bill. In the winter, we hung our wash in the basement. When we would beg her for a dryer, she would say she didn’t need one because that’s why God created sunlight.

If you left a light on after leaving a room, the repercussion was a long lecture about wasting electricity. Big Mama wouldn’t go to bed until she surveyed every room, making sure lights were turned off and appliances were unplugged.

Before you opened the refrigerator door, you’d better have had a good idea of what you wanted. Otherwise, you’d get another lecture for keeping the door open too long while you decided what to pull out. “What am I, made of money?” Big Mama would say.

She was smart about how much she drove, always conscious of cutting down unnecessary trips to save gas.

One of my colleagues said recently that her grandmother was the same way: “We make a big to-do about energy efficiency, but folks like my grandmother were green before it was a political statement.”

Her grandmother, my grandmother — the children of the Great Depression — were energy-smart because they had to be. So what happened to the generations that followed?

Many of us are lazy about energy consumption or indifferent to the personal and global costs because, compared with our huge mortgages, car and student loan payments, and credit card debt, our electric bills seem minuscule. But in low-income households such as the one my grandmother managed, the electric or gas bill meant something. For today’s low-income families, it still really hurts if that bill gets too high. But once you start ascending the economic ladder, energy costs aren’t so overwhelming that they force people to conserve more.

A dryer is typically the second-biggest electricity-using appliance after the refrigerator. Over its expected 18-year lifetime, the average clothes dryer will cost about $1,530 to operate, according to the California Energy Commission. Some families can drop that much money or more on one television.

As it turns out, our homes today are becoming more energy-efficient, according to the latest results of a residential energy consumption survey conducted by the U.S. Energy Information Administration, the statistical agency within the Department of Energy.

In 2005, energy use per household was 95 million British thermal units, compared with 138 million Btus in 1978, a decrease of 31 percent.

However, we have become energy hogs in other areas. In 1978, most households had only one television. In 2009, 44 percent of all U.S. homes had three or more sets, and more than 45 percent of homes have at least one television with a screen size of 37 inches or larger. Screen size and average energy consumption per television continue to grow, according to the EIA.

In 2009, more than 45 million households (40 percent) had a digital video recorder or DVR attached to the most-used television. That’s important because DVRs have largely replaced or supplemented VCRs and DVD players, which consume less energy per unit than DVRs. Over the past three decades, the portion of residential electricity used by appliances and electronics in U.S. homes has almost doubled, from 17 percent to 31 percent.

When was the last time you stopped to think about how much energy you use to charge and run all your new electronic gadgets?

Ernst & Young, which has provided consumer-market strategies to power and utility companies, says there is no compelling consumer proposition for being energy-smart.

So how can we encourage a culture of conservation among consumers?

Smart-energy campaigns should focus on persuading people to treat their energy usage like shopping for the best Black Friday deal or the lowest airline or hotel price. Consumers will spend hours on the computer trying to find a discount flight or hotel room. After all, this generation loves to hunt for bargains. We just have to get Americans to be as diligent about their energy consumption as they are about snagging a discount TV.

Big Mama was careful about her energy consumption because she had to be. But if we can’t get people to conserve based on economic hardship, appealing to their bargain-shopping instincts might work. It certainly gets them shopping at crazy hours on the day after Thanksgiving.

Readers can write to Michelle Singletary c/o The Washington Post, 1150 15th St., NW, Washington, D.C. 20071. Or e-mail: singletarym@washpost.com. Personal responses may not be possible. Please also note comments or questions may be used in a future column, with the writer’s name, unless a specific request to do otherwise is indicated.