Instituto Brasileiro de Geografia e Estatística

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National System of Consumer Price Indices

Technical note 02/2001

Methodology for Calculating the Price Changes of the Electrical Energy

The electric energy price change in the National System of Consumer Price Indices has been estimated, since its implementation, by means of a theoretical calculus associated with the household monthly average consumption in kw/h. The data sources are the Consumer Expenditure Survey and the prices obtained from the supply companies. The average consumption is specific for the target region and population of the INPC (families living in urban areas, with a salaried reference person and a 1-to-8-minimum-wage monthly income) and IPCA (families living in urban areas with a 1-to-40-minimum-wage monthly income).

The procedures for collection, calculus and incorporation of price adjustments are presented below:


The price of the kw/h and the ICMS tax over the bills of the different regions are monthly obtained from the supply companies. The date of the last adjustment of each component of the calculus and the information about the procedure of calculus of the bills are obtained as well.


Based on the replication of the procedure of calculus used by the supply companies for each consumption level, the value of the bill corresponding to the reference month is calculated. The price relative of the month is calculated by the ratio of the value of the reference month to the value obtained in the previous month.

Incorporation in the SNIPC

This relative is incorporated in the monthly indices in accordance with the criterion of application, that is, the impact of an adjustment on the result of the index depends on the day when it occurs. For example: if the adjustment of the kw/h occurs on the first reference day, this adjustment is entirely incorporated into the index. If the adjustment occurs in another date, the part incorporated in the reference month corresponds to the fraction (n/30) of the total adjustment, where n corresponds to the number of days from the adjustment date up to the last day of the month. The incorporation of the adjustment is considered in the calculus of the following month by means of the formula ((30-n)/30). That is valid for INPC and IPCA, which consider the prices collected in the civil month.

In the following table, we present the values (presently used in the calculus of electric energy in INPC and IPCA) of the kw/h household monthly average consumption for each region.

Average household consumption by area of INPC and IPCA

(Unit of measurement: kWh)

Rio de Janeiro 116 210
Porto Alegre 144 199
Belo Horizonte 160 212
Recife 109 151
São Paulo 211 249
Brasília 166 221
Belém 181 222
Fortaleza 104 143
Salvador 131 171
Curitiba 137 196
Goiânia 174 220

Source: SNIPC/ POF

The complete methodology of the indexes is presented in the document titled "Sistema Nacional de Índices de Preços ao Consumidor - Métodos de Cálculo", 4th edition, 1996. Sold at IBGE bookstores.