Water Source systems have the benefit of greater heat transfer capability. Water is 4 times more effective moving heat than air. Water in loops, lakes or rivers remain at a relatively low temperature compared to air (especially here in texas). The lower temperature of the water directly impacts performance due to the ease of moving heat into a low temperature medium (water) versus a high temperature medium (air).
The methods available to compare performance include comparing ratings for systems in both heating and cooling modes. Heat Pumps perform both functions and the ratings of water source systems include Energy Efficiency Ratios of 31.6 and Coefficients of Performance of 5.1 (Geocomfort YT).These flexible heating and cooling systems come standard with domestic hot water assist to help cut hot water costs 25% to 40% annually.