**Syntax**

BlockRate(Customers, TimestepsPerBillingPeriod, Rate_1, RateDenomUnit_1, UpperLimit_1, UpperLimitUnit_1, Rate_2, RateDenomUnit_2, UpperLimit_2, UpperLimitUnit_2, ..., Rate_N, RateDenomUnit_N)

**Description**

Tiered water pricing policies are often touted as a means of promoting demand management. Water conservation practices are motivated by increasing unit costs on higher usage of water. The BlockRate function allows for the approximation of revenues generated by such a block rate pricing structure. There is no limit to the number of blocks.

**Customers**: The number of customers
included in the demand site. Note: the block rate is calculated for the
average customer use--actual rates will differ slightly, because some
customers will use more than the average and some will use less, and the
block rate structure is inherently non-linear. WEAP will take the total
water used by the demand site and divide by the number of customers to
derive the average usage per customer. The block rates will be applied
to this average usage to get the average cost per customer. This average
cost will then be multiplied by the number of customers to get the total
customer cost.

**TimestepsPerBillingPeriod**: The
length of the billing period, in timesteps. E.g., for quarterly billing
and a monthly timestep, enter 3. WEAP will calculate the cost for each
timestep, by dividing the block sizes by this number of timesteps. For
example, instead of one bill every 3 months, there will be a bill every
month, but each will be approximately 1/3 of the quarterly bill.

The following four parameters are repeated for each block, except for the final block, which includes only the first two parameters (because it has no upper limit).

**Rate_i**: The cost of water for
block i, either a unit cost or a flat rate. See RateDenomUnit_i

**RateDenomUnit_i**: The denominator
unit for Rate_i (e.g., "gallons," or "cubic meters"),
or "flat" to indicate a fixed cost regardless of usage within
this block. A flat rate, or "base rate," is often charged for
the first block.

**UpperLimit_i**: The upper limit
water volume for this block. This parameter is not included for the last
block, because it has no upper limit.

**UpperLimitUnit_i**: The unit for
the upper limit water volume. This parameter is not included for the last
block, because it has no upper limit.

**Example**

The 100,000 households in South City are billed every 6 months, using the following block structure:

Base charge of $29.20 per bill includes up to 20,000 gallons

20,000 - 30,000 gallons at $1.40/1000 gallons

30,000 - 50,000 gallons at $1.65/1000 gallons

50,000 - 70,000 gallons at $1.90/1000 gallons

70,000 - 90,000 gallons at $2.25/1000 gallons

Over 90,000 gallons at $2.60/1000 gallons

The following expression should be entered in the "Variable Benefit" data tab for South City:

BlockRate(100000, 6, 29.20, flat, 20000, gal, 0.00140, gal, 30000, gal, 0.00165, gal, 50000, gal, 0.00190, gal, 70000, gal, 0.00225, gal, 90000, gal, 0.00260, gal)

Note that WEAP calculates the cost for each month, but because the bill covers 6 months, WEAP will divide the size of each block by 6. Also, the flat rate would be divided evenly over each of the 6 months. If, for example, the average customer use in January was 4000 gallons, this would fall in the second block: 20,000 - 30,000 gallons for 6 months is equivalent to 3333 - 5000 gallons for 1 month. 4000 gallons would be charged a flat rate of $4.87 for the first 3333 gallons, and $0.0014/gallon for the next 667 gallons. The cost per customer = $29.20/6 + (4000 - 3333) * $0.0014 = $5.80, or a total cost for all customers of $580,047.