Energy Savings

Per square foot of building space

The Efficiency Advantages of Using Water

Water is the most efficient way to move thermal energy. For example, a 2 inch [51 mm] water pipe can carry the same amount of cooling as a 24 inch [610 mm] air duct, requiring up to 90% less transport energy in the process and taking up far less space.

The mass of the water loop also provides thermal storage, allowing a substantial amount of heat to be carried from occupied periods into morning warm-up. There is no storage benefit in most HVAC systems.

Water-source heat pump heat exchangers are more compact and efficient than air-cooled heat exchangers because of the much higher mass and thermal conductivity of water, providing closer approach temperatures and higher heat pump efficiencies.

Water-source heat pumps also operate at lower condensing temperatures because they are linked to the outdoor wet bulb temperature (using a cooling tower) or the deep earth temperature (using a ground heat exchanger) instead of the higher outdoor dry bulb temperature, again leading to higher efficiencies and longer service life.

 Water-Loop Energy Sharing

Buildings contain year-round sources of thermal energy (internal heat gains). Read more about how water-source heat pump systems recover and recycle a building’s thermal energy.

Recent Improvements Mean Even Higher Efficiencies

In the mid-1990s, EER (Energy Efficiency Ratio) was 12 to 14. Now, the best water-source heat pumps are 18 to 20 EER, with two-stage units operating at a remarkable 27 EER.