Definition: Energy Performance Index
What Is the Energy Performance Index?
Energy Performance Index is the measure of the total energy consumption in a building divided by the gross floor area in square meter. The unit of measure is kWh/m2.
The objective of this index is to develop a quantitative energy efficiency metric, based on actual measurement as well as accurate prediction of energy consumption.
BEE Star Rating for Buildings
Bureau of Energy Efficiency, Ministry of Power, Government of India has a Star Rating System for buildings rated on the basis of EPI similar to the popular ratings provided by the same organization for consumer durable applicances.This programme would rate buildings on a 1-5 Star scale with 5 Star labeled buildings being the most efficient. Five categories of buildings – office buildings, hotels, hospitals, retail malls, and IT Parks in five climate zones in the country have been identified. The Reserve Bank of India’s buildings in Delhi and Bhubaneshwar, the CII Sohrabji Godrej Green Business Centre and many other buildings have received BEE 5 star ratings.
As per a press release of Infosys, the Pocharam, Hyderabad Campus of the IT giant which has been recognized globally as one of the greenest campuses with world-class innovation in sustainability has an EPI of 75 kWh/m2 per annum which is among the lowest in the industry globally and is a benchmark for others to achieve.
How EPI Is Calculated
EPI is calculated by dividing a building’s total annual energy consumption (in kWh, usually taken from electricity bills plus any other fuels converted to kWh) by its built-up or gross floor area in square metres. As an illustration, a building that uses 1,000,000 kWh in a year across 10,000 m² of floor area has an EPI of 100 kWh/m² per year. A lower EPI means the building delivers the same floor space with less energy.
Because EPI is based on measured consumption, it is only meaningful when compared with buildings of a similar type and climate. A hospital running round the clock will naturally use more energy per square metre than an office that is occupied only during the day, which is why BEE rates buildings within categories and climate zones.
Why EPI Matters for Smart Buildings
EPI gives building owners, facility managers and city authorities a single, easy-to-track number for energy efficiency. It helps them benchmark a building against its peers, set reduction targets, and check whether retrofits are actually saving energy. In smart buildings, a building management system (BMS) and energy meters can track consumption continuously, so EPI can be monitored month by month rather than worked out once a year.
Ways to Improve a Building’s EPI
- Optimise HVAC, usually the largest energy load, with scheduling, variable speed drives and set-point controls through a BMS.
- Switch to LED lighting with occupancy and daylight sensors.
- Improve the building envelope with insulation, shading and better glazing to cut cooling loads.
- Sub-meter major loads to find where energy is being wasted.
- Add on-site renewable energy, such as rooftop solar, to reduce grid consumption.
India’s Energy Conservation Building Code (ECBC), also developed by BEE, sets minimum energy performance requirements for new commercial buildings. It works alongside EPI-based star ratings to push buildings towards lower energy use.
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