There are nearly 60 thousand Mosques spread across the Kingdom of Saudi Arabia, consuming nearly 3 Terawatt-Hour of site electrical energy, 70% of which is due to the use of mostly inefficient HVAC systems. It is estimated that 20 million M3 of expensively treated water used annually for ablution, 50% of which flows directly to the drain without any contamination. This paper evaluates the potential savings in water and energy of reusing ablution water to run mosque Air-Conditioning systems using high efficiency IDEC technology.