sentences:  A study in 2012 that focused on 479 green infrastructure projects across the United States, found that 44% of green infrastructure projects reduce costs compared to the 31% that increased the costs.The most notable cost savings were due to reduced stormwater runoff and decreased heating and cooling costs.A comprehensive green infrastructure in Philadelphia is planned to cost just $1.2 billion over the next 25 years, compared to over $6 billion for "grey" infrastructure (concrete tunnels created to move water).