Energy efficiency represents the efficiency of the entire network to convey water from the supply point through the distribution system and ultimately to the customer, in terms of potential energy converted to friction, discrete loss and losses at the customer tap. A large percent of energy input to a water network is lost through pipe friction or control such as pressure reduction. Energy loss is wasteful in systems requiring pumping. In gravity systems, it is a potential free energy source that, in many cases, is lost.

In an ideal network, every customer would receive exactly the right supply pressure at minimum energy cost. Sustainability modeling will calculate this cost by post processing network model hydraulic results and comparing the ideal against actual energy loss.

The energy efficiency in a distribution system is comparable to measures such as pump or turbine efficiency, in that there is always an inevitable energy loss within the system and 100% efficiency can never be achieved. In concept, energy efficiency can be described as a measure of energy used to get water from the source to the customer. The energy efficiency helps to highlight those areas with the greatest potential for improvement. It is most useful in planning energy optimization across a utility's entire zone of operation. With proper application and development, the Sustainability function can be used to identify energy savings in:

• Pumped systems;

• Gravity systems;

• Pumped – Storage systems

From the reservoir to customer, it is commonplace to waste a large proportion of the accumulated potential energy through pressure management (i.e., Pressure Reduction). This is practiced in part for leakage control measures and delivery pressure management. Little consideration is usually given to managing or accounting for the huge potential energy embodied in water at elevation. Pumped systems will normally attempt to optimize energy input by ensuring that pumped pressure is not excessive. However, some pumped systems are pressure reduced in order to maintain a minimum level of service pressure to the highest customers while reducing high pressures in the lower regions.

Some losses are introduced deliberately through pressure management at discrete locations such as pressure reducing or flow control valves. With sustainability analysis, water utilities have the potential to better manage these losses.

By far the greatest loss of energy is at the customer tap. As a result, customer consumption must be considered an unavoidable loss. Normally utilities use a targeted minimum delivery pressure to provide the customer with reasonable service pressures. Ideally all customers would receive the water that they need at exactly the right pressure. However, it is not practical to maintain the minimum pressure at every single customer without loosing the potential energy.

Sustainability analysis provides an energy audit of a distribution network that could be utilized to prioritize investigations such as:

Run a Sustainability Analysis

To run the Sustainability calculation, you must start with a working EPS model. The energy audit calculation is based entirely on the hydraulics of the base model. Use the following procedure: