Managers at the Park Inn hotel at Heathrow claim that its new £14m conference centre is a paragon of energy efficiency. Structurally, the building uses a number of design initiatives that minimise energy wastage, but the Rezidor Hotel Group, which owns the Park Inn, has another way of going green: by joining its Goldpoints Plus loyalty system, guests earn points that can be used to offset greenhouse gas emissions through Rezidor partner the CarbonNeutral Company. It's a responsible pledge, but Rezidor's motives aren't purely altruistic—they'd like a pat on the back from responsible guests, too.

But do green initiatives like these actually boost hotel occupancy rates? According to a January 2007 survey conducted by the Association of Corporate Travel Executives (ACTE), only a third of companies have corporate travel policies that promote sustainable travel. The survey also found that controlling costs was a far more important factor than harm to the environment. Research by the International Hotels Environment Initiative backed up that assertion, finding that hotels which have not yet adopted environmental programmes are missing out on savings of between 10 and 40 per cent on energy bills, 25 per cent on waste and 20 per cent on water bills.

When the Park Plaza Riverbank on London's Albert Embankment first opened in 2005, monthly utility bills totalled around £67,000, according to Dave Bell, the hotel's chief engineer. Since then, he has deployed a number of green technologies that have brought that total down considerably.

Bell has fitted a device called the eCube to each of the hotel's 140 major fridge and freezer units at a total cost of £2,000. The units use 30 per cent less energy, saving £17,000. An energy management system regulates the hotel's boilers, cutting gas consumption by 35 per cent, saving £60,000 per year, he says, and a new type of lamp from Phillips has been fitted throughout the hotel, saving the hotel an added £25,000 per year.

Cost savings aside, these efficiencies still have an enormous effect on the hotel's carbon footprint, insists Alistair Watts, European marketing director of Park Plaza Hotels—and that, he argues, is increasingly important in attracting business travellers. "We're starting to see a lot of RFPs [requests for proposals] from corporate clients that ask us to outline our green credentials," he says. Pia Heidermark-Cook, director of responsible business for Rezidor, goes further still. She says that "for years", large corporate clients such as Tetrapak, Volvo and UBS have expected to be able to see Rezidor's environmental policy when negotiating rates for their executives with the hotel chain—and their requirements are becoming more and more stringent.

Rezidor's environmental policy now incorporates quarterly measurement of energy consumption at both hotel and corporate level, says Heidermark-Cook. "In 2006, our energy consumption per square metre was reduced by eight per cent compared to 2005," she says.

Critics say that the hospitality industry makes too much of isolated achievements while at the same time failing to deliver on company-wide enforcement of green policies—and that, they say, amounts to a "greenwashing" exercise that is being perpetrated on a global scale. In March 2006, for example, Hilton Hotels and Starwood Hotels and Resorts—two companies that actively promote their green credentials—were both kicked off the FTSE4Good ethical investment index for failing to meet its environmental criteria.

In their defence, hotel companies claim that their industry is more fragmented (across both brand lines and geographies) than most. And, "while it is becoming more common to find new hotels being developed with greenness built in," says Heidermark-Cook, "it is not always easy to retrofit an older hotel with the latest environmental technology."

In addition, there is no one standard for "environmental friendliness", just a vast array of overlapping efforts from local projects. In fact, the one international standard applicable to companies across all industry sectors—ISO 14001—has been largely ignored by the hotel trade.

To date, certification has been achieved by only a handful of UK hotels—the first being the Hammersmith Novotel, as recently as October 2006. Until corporate travel buyers get tougher on those hotels ignoring these standards, it's likely that many of the sector's environmental efforts will amount to little more than hot air.