Indian Seasonal Energy Efficiency Ratio (ISEER): An overview

The Government of India established the Bureau of Energy Efficiency (BEE) in 2002, under the provisions of the Energy Conservation Act, 2001. One of the objectives of BEE was to reduce energy intensity within the Indian economy and to promote the use of energy efficient equipments and devices. To promote energy efficiency and conservation, BEE introduced star rating system (varying from 1-5) for various electrical appliances such as air conditioners (fixed & variable speeds), ceiling fans, colour televisions, direct cool refrigerators, frost-free refrigerators, LED lamps, water heaters, washing machines, etc., based on their power consumption. The star rating system is a labelling system, under which the manufacturer is required to place a label indicating how much electricity the appliance is likely to consume under pre-set conditions. 

Previously, star rating of ACs in India worked using the Energy Efficiency Ratio (EER). EER is the ratio of cooling capacity to power input. Air conditioners with higher EER are preferred, as these are more efficient. Usually, EER of an air conditioner is measured under a specific condition i.e. 35 degrees C, outdoor temperature; 27 degrees C indoor temperature and 50% relative humidity.

In many countries, the Seasonal Energy Efficiency Ratio is used for calculating the energy efficiency of the air conditioner. As there is season-wise variation in temperature, the amount of cooling and consequently, the amount of energy required, will also vary from season to season.

Taking this into consideration, BEE has defined Indian Seasonal Energy Efficiency Ratio (ISEER) for ACs as a star rating method for India from January 2018. ISEER is the ratio of Cooling Seasonal Total Load (CSTL) to Cooling Seasonal Energy Consumption (CSEC) i.e. the ratio of the total annual amount of heat that the equipment can remove from an indoor space when operated in active mode to the total annual amount of energy consumed by the equipment during the same period. Energy efficiency of an AC has been calculated based on average performance at outside temperatures between 24 and 43 degree C based on Indian weather data.

To calculate the annual electricity consumption of an AC, it was assumed that an AC will run for 1600 hours throughout a year. The annual temperature profile used is based on weather profile for 54 cities across India, by The Indian Weather Data Handbook, 2014. Below is the temperature distribution used:

Table 1: Reference outdoor temperature bin distribution - National weather data

The star ratings of ACs (From 1st January 2018 to 31st December 2019)  are given below:

Table 2 and Table 3 describe star ratings for window ACs and split ACs respectively. For the purpose of upgrading the minimum energy performance level of window air conditioners, BEE has announced that 1 star rated window air conditioners (as specified in Table 1) should not be manufactured from January 1, 2018. Therefore, window air conditioners only with 2 to 5-star ratings will be available until December 2019.

Star rating has become mandatory for all ACs and because of this, the energy efficiency of air conditioners has increased over the years. If the trend continues, air conditioners should not be a big strain on consumers’ pockets.