Seasonal Proration

Seasonal proration adds another layer of complexity. If calculation rules are specified to prorate seasonally, the seasonal period specified on a given seasonal calculation rule dictates how a calculation rule's value or associated service quantity is prorated.

There are two proration methods, Prorate and Prorate Seasonal SQ, which may be specified on seasonal calculation rules. Both of these proration methods behave the same way with respect to calculation rule value proration. If a given seasonal calculation rule is eligible for Calculation Rule Value Proration, the ratio of days in the season that are applicable during the calculation period to the days in the calculation period determines the seasonal factor. When it comes to service quantity proration, the two proration methods are different. If a given seasonal calculation rule is eligible for Service Quantity Proration, it prorates the service quantities as follows:

• Prorate. A seasonal factor is calculated as the ratio of days in the season that are applicable during the calculation period to the days in the calculation period. This ratio is applied along with the consumption period factor and calculation period factor to determine the prorated service quantity.
• Prorate seasonal SQ. In this case, it is assumed that either the meter measures seasonal consumption on separate registers or the consumption has been split into separate service quantities by other means (like an SQ rule). To determine a prorated seasonal service quantity, the seasonal proration factor is calculated as for a Prorate seasonal calculation rule. The seasonal factor is then multiplied by another ratio of total consumption period days to days in the season that are applicable for the total consumption period. This modified seasonal factor is applied along with the consumption period factor and calculation period factor to determine the prorated service quantity.

Example ( Prorate ):

Let's say that 600 kWh and 50 kW are the billable service quantities for a consumption period from April 1 to April 30. Prorate seasonal calculation rules are defined on a monthly rate that charge $0.05 per kWh and $0.75 per kW from January 1 to April 15. Prorate seasonal calculation rules are defined on the same rate version that charge $0.06 per kWh and $0.80 per kW between April 16 and December 31. Assume only one rate version is effective for the consumption period.

• The consumption period factor is 1 (not applicable).
• The calculation period factor is 1.0.
• The seasonal factor for the kWh calculation rule whose season is effective from January 1 to April 15 is 0.5 (15 season days in calculation period / 30 days in the calculation period).
• The resulting bill calculation line uses service quantity proration:
• 600 kWh x 0.5 (seasonal factor) x $0.05 = $15.00.
• The seasonal factor for the kW calculation rule whose season is effective from January 1 to April 15 is also 0.5.
• The resulting bill calculation line uses calculation rule value proration:
• 50 kW x $0.75 x 0.5 (seasonal factor) = $18.75.
• The seasonal factor for the kWh calculation rule whose season is effective from April 16 to December 31 is 0.5.
• The resulting bill calculation line uses service quantity proration:
• 600 kWh x 0.5 (seasonal factor) x $0.06 = $18.00.
• The seasonal factor for the kW calculation rule whose season is effective from April 16 to December 31 is also 0.5.
• The resulting bill calculation line uses calculation rule value proration:
• 50 kW x $0.80 x 0.5 (seasonal factor) = $20.00.

Example (Prorate seasonal SQ):

Let's say that a given meter measures winter consumption separate from summer consumption. The meter itself measures kWh/summer on a register between June 21 and September 18, and measure kWh/winter on another register at other times of the year.

We are generating a bill segment with a consumption period from September 2 to October 30. A monthly rate schedule has two rate versions effective during the consumption period. The latest rate version is effective on October 1.

Each of the rate version calculation groups have Prorate seasonal SQ seasonal calculation rules defined. The first rate version's calculation rules charge $0.06 per kWh/summer and $0.05 per kWh/winter. The second rate version calculation group has a single calculation rule that charges $0.05 per kWh/winter.

Assume that the billable service quantities are 800 kWh/summer and 1600 kWh/winter.

First set of bill calculation lines (September 2 to September 30):

• The consumption period factor is 30 normal days / 60 consumption days = 0.5.
• The calculation period factor is 30 calculation days / 30 normal days = 1.0.
• calculation rule 1 ($0.06 per kWh/summer):
• The seasonal factor 17 seasonal days / 30 calculation days = 0.5666667.
• The modified seasonal factor is 0.5666667 x 60 consumption days / 17 seasonal days = 2.0.
• The resulting bill calculation line:
• 800 kWh/summer x 0.5 (consumption period factor) x 2.0 (modified seasonal factor) x $0.06 = $48.00.
• calculation rule 2 ($0.05 per kWh/winter):
• The seasonal factor is 12 seasonal days / 30 calculation days = 0.4.
• The modified seasonal factor is 0.4 x 60 consumption days / 42 seasonal days = 0.571428.
• The resulting bill calculation line:
• 1600 kWh/winter x 0.5 (consumption period factor) x 0.571428 (modified seasonal factor) x $0.05 = $22.86.

Second set of bill calculation lines (October 1 to October 30):

• The consumption period factor is 30 normal days / 60 consumption days = 0.5.
• The calculation period factor is 30 calculation days / 30 normal days = 1.0.
• Calculation rule 1 ($0.05 per kWh/winter):
• The seasonal factor 30 seasonal days / 30 calculation days = 1.0.
• The modified seasonal factor is 1.0 x 60 consumption days / 42 seasonal days = 1.428571.
• The resulting bill calculation line:
• 1600 kWh/winter x 0.5 (consumption period factor) x 1.428571 (modified seasonal factor) x $0.05 = $57.14.