http://www.districtenergy.org/what-is-district-energy/

District energy systems produce steam, hot water or cooled water at a central location. It is then piped underground to individual buildings for space heating, domestic hot water heating and air conditioning. This removes the need for individual systems.

The district energy system provides benefits like:

• Improved energy efficiency
• Enhanced environmental protection
• Fuel flexibility
• Ease of operation and maintenance
• Reliability
• Comfort and convenience for customers
• Decreased life-cycle costs
• Decreased building capital costs
• Improved architectural design flexibility