My colleague Steven has been nagging me for months to replace the halogen floor lamp in my office. It’s not that he finds it unattractive—this nice-looking modern fixture does add ambience to an otherwise drab room. Rather, Mr. Know-It-All tells me, this fixture is an energy hog and chows down far more electricity than a lamp that uses compact fluorescent lightbulbs and even incandescents. Indeed, this fixture can cost up to $100 to run each year.

Thank goodness Steven hasn’t seen my aquarium at home. Sure, it’s kind of dirty since I dread cleaning it, but I’m more concerned he’s going to howl about how much electricity the equipment uses since some aquarium gear can consume as much juice as a refrigerator.

How’d I find this energy-consumption information? I ran an energy audit with the Home Energy Saver (shown). This calculator from the U.S. Department of Energy estimates home energy use and carbon-dioxide emissions and provides you with advice on how to reduce both.

It’s a pretty neat tool. I plugged in my ZIP code and within seconds found out that the average house in my New York City suburb spends $2,267 annually on energy—nationwide the average is about $1,300—while an energy-efficient home there spends $1,451.

Entering a bit more information got me a more-accurate estimate of my energy use—I actually spend about $3,000 a year—and a laundry list of changes to consider, such as replacing halogen and incandescent bulbs with CFLs where possible in high-use fixtures (there you go, Steven), insulating boiler pipes, installing an Energy Star–qualified programmable thermostat, and upgrading my refrigerator, dishwasher, and heating system to new, more-efficient models.

By making all of these changes, according to the calculator, I could save almost $1,500 a year. Since I’m not planning on moving anytime soon, I really need to boost the energy efficiency of my old house . . . and stop wasting money.—Kimberly Janeway

Essential information: Read our expert advice for 10 easy ways to save hundreds of dollars on household energy costs.