How does rainwater harvesting reduce energy costs in HVAC systems?

Rainwater harvesting reduces energy costs in HVAC systems by providing a free source of water for cooling towers, evaporative coolers, and ground source heat pumps. This reduces the energy required to treat and transport potable water, which can account for up to 20% of a building’s total energy consumption. Furthermore, using rainwater for irrigation can reduce the energy required for pumping and treating water.