Q: When I stay at a hotel there is always a note that a towel hung up will not be replaced, thereby saving on water. However, I come back to my room and it always appears that the towel has been replaced. Do hotels actually do this or is the note there just to appear environmentally conscious? Also, is there a website that ranks which hotels recycle newspapers, plastic bottles, reduce heating and air conditioning, etc.?

Asked by Cathy Clonts, London, England

Do towel- and linen-reuse programs make a difference? The Association for Linen Management estimates that hotels can save up to $6.50 a day per occupied room with such programs. The actual money saved depends on factors including local utility prices, laundry wages and the type of washer and detergent used by the hotel. In any case, the savings add up quickly. Assume that a 200-room hotel with a 55 percent occupancy rate implements a towel/linen reuse program. At $6.50 per occupied room, that would be $260,975 saved per year. That savings helps explain why so many hotels have adopted towel/linen reuse policies, even without the environmental consideration.

No matter what motivates the hotel you choose, you can still rest easy knowing that your participation in a towel/linen reuse program contributes to water conservation and less detergent use. The website Economically Sound estimates that a 150-room hotel can conserve 6,000 gallons of water and 40 gallons of laundry detergent per month with a towel/linen reuse program. That's 72,000 gallons of water and 480 gallons of laundry detergent per year. That means that even a relatively modest hotel can save the equivalent of three people's annual water use each year just by having a towel/linen reuse program. In large hotels, like the Bellagio Hotel in Las Vegas (which has 3,933 guest rooms and suites), the towel/linen reuse program could be saving more than 150,000 gallons of water per month. Not that that—or the LED lights in the slot machines—actually makes anything about Las Vegas sustainable, but still. . . .

Towel and linen reuse programs are just the first steps to minimizing the environmental impacts of the hotel industry, which faces most of the same environmental challenges as homeowners, on a vastly larger scale. That larger scale—and its bottom-line implications—often provides the incentive for hotels to conserve energy and water and to minimize waste, while homeowners might not pay as much attention to money squandered on utility bills.

Hotels can go beyond simple steps such as installing energy-efficient lighting and low-flow showerheads. It's hard to see too many homeowners installing keycard-based energy management systems at home, but many hotels have done so. Guests must insert their hotel keycard into a control switch near the door in order to turn on the lights and HVAC systems—and when the guest leaves the room, all those energy suckers go dead. According to Green Lodging News, when the Westin hotel in Pittsburgh invested in a keycard system for $120,000, they made the money back in energy savings in just 10 months.

Even modest improvements can add up to major environmental and economic savings when they're carried out across entire hotel chains. Thanks to an energy management program, the lodging company Marriott International shaved off 3 percent of its greenhouse gas emissions per available room in 2008, saving $1.3 million in the process. As a whole, the federal government's Energy Star program estimates that reducing energy use across the lodging industry by 10 percent could save $745 million a year.

That's fine for the hotels—and not half bad for the planet. But what can we do as travelers to promote still-more environmentally conscious options? The first step is probably seeking out hotels that go beyond the simple towel/linen reuse policies and incorporate sustainable practices into everything from construction to waste management.

Green certifications could use a little clarification, to be sure. But most are at least a good indication that a hotel is trying to do more than just save a dollar or two per room. For example, the Green Key eco-rating program examines hotels in nine areas of sustainability practices: energy conservation, water conservation, solid waste management, hazardous waste management, indoor air quality, community outreach, building infrastructure, land use and environmental management. Based on this assessment, the hotel is awarded up to five "keys"—the more keys, the more sustainable the hotel.

The difficulty with these certification programs is that there are a lot of them and it is not always apparent what they mean. While the certification may be meaningful in many cases, some certification programs may be more lax in their criteria, or hotels may not fulfill certain promises made in certification. Some standardization has begun to take form, with statewide certification programs in numerous states. As of yet, a nationwide standard has not been developed, although the Environmental Protection Agency is working on federal certification program.

Hotels respond to consumer demand, so it's important to let your hosts know that lower-impact lodging is important to you. But travelers can do more than just complain or compliment—we can take action. Many of these actions are just what you would do at home, such as turning out the lights when you leave the room and making sure you've powered down the TV, home office and other energy-drawing machines back home before your trip. Choosing less polluting methods of travel can have a large impact on your trip's overall carbon footprint. Trains emit much less carbon dioxide than airplanes, while biking and walking around your destination, rather than driving, is an obviously beneficial choice.

I suppose if you want to be truly sustainable, you should stay home and tend your organic garden. But what's the use of preserving a healthy planet if you don't get to get out and enjoy it? When it's time to roam, just remember that there are plenty of choices available to travelers who want to minimize their environmental impact. And if you want to keep things simple, just do what you would at home—turn out the lights and don't forget to hang up that towel.

REESE ROGERS plans to receive his bachelor's in Human Biology in 2010 and his master's in Earth Systems in 2011.