Researchers Peter H. Gleick and Heather Cooley at the Pacific Institute in California have published research which shows that bottled water requires as much as 2,000 times more energy to produce than tap water.

Gleick and Cooley calculated the energy requirements for various stages in bottled water production, including manufacturing the plastic bottles, processing the water and the bottles, and transporting and cooling the final product. 

Combining the energy for these stages, the analysis finds that producing bottled water requires between 5.6 and 10.2 megajoules of energy per litre of water – up to 2,000 times the energy cost of tap water, which takes about 0.005 megajoules per litre to treat and transport. Around 50 million barrels of oil per year are used just to produce the plastic bottles – very few of which are currently made from recycled material.

For water transported short distances, the energy requirements are dominated by the energy to produce the plastic bottles. Long-distance transport, however, can lead to energy costs which are even higher than the energy to produce the bottle.

In fact, most bottled water is "purified water"  – produced by treating and bottling ordinary municipal water in major cities for local distribution. "Spring" water is packaged at a specific location, for example Evian water is packaged in France, and transported to markets around the world. Transportaton of Evian water to New York consumes 5.8 megajoules per litre of energy of water.