• IRWD's allocation-based conservation rate structure uses property-specific water budgets and tiered pricing to provide customers with an economic incentive to encourage efficient water use. 
   
• Allocation-based conservation rate structures are fair. They reward those who use water wisely and shift the costs associated with water over-use to those that waste water. 
   
• IRWD's Allocation-based conservation rate structure provides our customers with the water they need at some the lowest rates in Orange County. When more water is used than a customer is allocated higher rates are charged. The revenue collected from those overuse rates is then used to support conservation, environmental programs, and for the costs associated with additional water supply purchases.
   
• Allocation-based conservation rate structures have a proven track record. When IRWD implemented this rate structure in the Irvine Service Area, the area experienced a significant drop in water consumption while, at the same time, the health of landscapes improved.

• IRWD’s rate structure takes into consideration both indoor and outdoor water use.  
   
• Allocations are based on the number of residents in the home, the type of home (detached home, attached home or apartment), landscape square footage and actual daily weather and associated evapotranspiration (ET) data.
   
• ET is the amount of water that is lost by plants through evaporation and transpiration, and which needs to be replaced for the plants to remain healthy.
   
• Grass is typically the highest water-using plant in a landscape. Trees and shrubs use far less water than grass – but IRWD’s allocation system will assume that almost your entire landscape is covered with grass.
   
• Your allocation should provide more than enough water to meet the demands of your landscaping.
   
• The base allocation formula assumes the following:

Detached home (i.e. single family home): 4 people with 1300 square feet of landscaping

Attached home (i.e. condominium or townhouse): 3 people with 435 square feet of landscaping

Apartment: 2 people with no landscaping 

• Variances are available to make adjustments to the allocation for more people living in the home, medical needs, livestock, additional landscape or other special circumstances. IRWD has used parcel and other data to automatically calculate landscape variances for Santiago area customers.

• IRWD’s rate structure is site specific, taking into consideration production needs, number of employees, water use efficiency practices and irrigation needs.
   
• Many commercial businesses have separate water meters for indoor use and outdoor landscaping – in these cases, the allocations are handled separately.
   
• Commercial, Industrial and Institutional water allocations are referred to as a Base Index.
   
• The Base Index is determined from actual historical water usage for each individual customer.
   
• Your initial Base Index will be calculated by averaging the past three years water use for each month.
   
• The monthly water bill is calculated by comparing actual usage with the base index.
   
• When a business grows, adds more employees, increases manufacturing output or serves more customers, customers may request a base index evaluation for possible adjustment of the base index.

• IRWD’s rate structure is based on science, taking into consideration landscape acreage and the actually daily weather and evapotranspiration (ET) data.
   
• ET is the amount of water that is lost by plants through evaporation and transpiration, and which needs to be replaced for the plants to remain healthy.
   
• The system provides ample water for healthy landscaping.
   
• Implementation requires accurate information on irrigated acreage.

The most updated information about IRWD's rates can be found in IRWD's Rates and Charges.

For the typical residential customer in the Santiago Rate Area, with a 5/8’ meter, the monthly water bill should see a decrease of approximately 40 percent. The decrease is attributed to lower charges for the water service and commodity charges.