EVER WONDERED HOW YOUR ESTIMATED ELECTRICITY BILL IS CALCULATED?

Available data shows that of all the electricity consumers in Nigeria about 60% majority still have no electricity meters. That is, they have neither the prepaid meters that operate with vouchers nor the old fashioned post-paid meters that are supposed to be read before bills are issued. Hence, most electricity consumers have no meters at all and the electricity bills are simply estimated.

Granted that the Nigerian Electricity Regulatory Commission (NERC) has severally ordered the Distribution Companies to provide every electricity consumer with a meter, they have also made regulation for the estimation of bills for unmetered consumers pending when they are metered. This Regulation is called the NERC Methodology for Estimated Billing, 2012 which every Distribution Company has an obligation to comply with in the estimation of electricity bills.

This Regulation categorises consumers into two for the purpose of the estimation of their electricity bills. The two categories are:

Unmetered Maximum Demand Customers – The following tariff classes are under this group and this is indicated on the Bill issued to such customers as follows: Residential (R3, R4); Commercial (C2, C3); Industrial (D2, D3); and Special i.e. religious houses, agro enterprises, water boards, government hospitals and institutes (A2, A3)..

Unmetered Non-Maximum Demand Customers – The following tariff classes are under this group and this is indicated on the Bill issued to such customers as follows: Residential (R1, R2); Commercial (C1); Industrial (D1); Special i.e. religious houses, agro enterprises, water boards, government hospitals and institutes (A1) and Street Lights (S1)

BILLING OF UNMETERED MAXIMUM DEMAND CUSTOMERS

The billing of unmetered Maximum Demand Customers is based on “Load Measurement Method” which is the measurement of voltage and current on the customer’s premises for a specific period between one to twenty four hours during normal operation and the application of the following formula:

Kwh = √3 × V₂ × I₂ × PF × Av × LF × 1000

Where:

V₂ = Line Voltage in Volts

I₂ = Line Current in Amperes

PF = Power Factor

LF = Load Factor

Av = Number of hours of power supply availability in the month.

Amount payable = (Tariff Class rate × kwH) + Fixed Charge + VAT

BILLING OF UNMETERED NON-MAXIMUM DEMAND CUSTOMERS

In calculating estimated bills for unmetered non-maximum demand customers for the tariff classes under this group, the principle applied here is the “weighted average cluster load”. Under this method, the load of the entire metered customers at a feeder is subtracted from the total energy supplied to the feeder (such as 33kv, 11kv feeders etc). Your feeder is located at the transformer you are connected with. Then there is an application of an appropriately determined availability factor and correction of losses which is now applied across the various classes and number of customers on each feeder.

This method also requires the determination of the average consumption of various classes of customers in the urban and rural areas. The relationship derived is applied to determine the proportion of the energy supplied to the feeder which is then proportionately distributed among the various customers.

Energy available for billing at the feeder for both metered and unmetered customers is calculated as follows:

Z = X - µX

Where Z is energy available for billing;

          X is energy on all feeders; and

µ is the percentage distribution technical loss currently put at (10% under MYTO)

How each of the bills is calculated using R1 customers as an example

R1 = ƪc R1 Zu/N R1

Where ƪc R1 is the weighted class average for R1 consumers

          Zu total energy used by unmetered consumers at the feeder

          N R1 total number of R1 consumers connected at the feeder

Same formula applies to the other non-maximum demand consumers as follows:

R2 = ƪc R2 Zu/N R2

Next time your estimated bill increases by any percentage, here are the things to check for:
(1)Percentage change in tariff (if NERC has increased the tariff) - tariffs  are printed on bills 
(2)Percentage increase in electricity supplied to your area
(3)Percentage reduction in the number of unmetered power consumers at your feeder
(4)Whether the transformer in locality has been replaced with another one of bigger capacity

If these factors have remained the same, while your utility bill has increased then you may be have a ground to query your bill. If there is an increase in these factors apart from (3) then your utility bill can justifiably increase by the percentage of change in these factors. If the reverse has been the case then your estimated bill should decrease else you have a ground to query it. 

In our next post we will let you know the prevailing tariff for your tariff class and how to estimate if your next estimated bill will be lower or higher than the last one you got.