Changing towels upon request.
Source:http://www.scientificamerican.com/media/inline/greening-up-the-hotel-industry_1.jpg
The Berghotel Muottas Muragl in Switzerland, the first eco-friendly hotel in the Alps, features a 750 m long solar panel system.
Source: http://www.muottasmuragl.ch/en/
Thermal loops at the lower level of the Berghotel Muottas Muragl, for supplying geothermal energy and storing any extra solar gain.
Source: http://www.muottasmuragl.ch/en/