The Energy Efficiency Index (EEI) is a metric used to assess the energy efficiency of certain electrical appliances and other energy-consuming products. It compares a product’s energy consumption with a standardized reference value.
The basic idea is simple: the lower the EEI, the less energy the product consumes compared with the applicable reference value when performing a specific process.
However, an important detail is often overlooked: there is no single EEI calculation formula that applies to all types of household appliances. The European Union specifies separate calculation methods for different product groups. As a result, the reference consumption, test conditions, weighting factors, and threshold values used to determine energy efficiency classes may differ between a washing machine, refrigerator, dishwasher, television, or another product.
The European Commission currently regulates a wide range of products through energy labeling and ecodesign regulations. These include refrigerators, washing machines, dishwashers, dryers, ovens, electronic displays, light sources, air conditioners, and many other energy-consuming products.
What Does EEI Stand For?
EEI stands for “Energy Efficiency Index.”
In its simplest form, the index can be expressed as:
EEI = (Actual or measured energy consumption / Standard reference energy consumption) × 100
For example, an EEI of 50 generally means that the product’s calculated energy consumption is 50% of the applicable reference energy consumption.
Therefore, an EEI of 30 indicates greater energy efficiency than an EEI of 60, provided that both values refer to the same product category and have been calculated using the same methodology.
It is important not to compare EEI values from completely different product types as though they represented exactly the same measurement. An EEI of 40 for a refrigerator and an EEI of 40 for a washing machine do not necessarily indicate the same level of efficiency. This is why energy efficiency classes, such as A through G, are defined using product-specific requirements and different applicable EEI ranges.
Why Is a reference value used?
A simple comparison of the energy consumption of different household appliances can be misleading.
Consider two refrigerators:
- Refrigerator A consumes 150 kWh per year.
- Refrigerator B consumes 180 kWh per year.
At first glance, Refrigerator A appears to be more energy-efficient because it uses less electricity.
However, suppose Refrigerator A has a capacity of 200 liters, while Refrigerator B has a capacity of 350 liters. These appliances offer significantly different storage capacities and, naturally, may require different amounts of electricity to operate. When their capacity is taken into account, Refrigerator B can actually be the more efficient appliance.
The same principle applies to washing machines. A 4 kg washing machine and a 10 kg washing machine cannot be objectively compared based solely on how much electricity they consume per cycle. The larger machine can use more electricity while also washing significantly more laundry.
The Energy Efficiency Index (EEI) helps address this problem by comparing an appliance’s energy consumption with a standardized reference value established for its particular product category.
There is no universal EEI formula that applies to all household appliances.
Instead, each regulated product group has its own calculation method, reference values, test conditions, and other parameters. For example, for household washing machines, the current EU methodology uses the weighted energy consumption of the “Eco 40–60” programme and compares it with the standard energy consumption for the same type of cycle.
The calculation is defined in the regulation as:
EEI W = (E W / SCE W) × 100
The letter W in EEI W identifies the calculation used for washing machines. Other product categories use their own definitions, reference values, and calculation methods.
How is the Energy Efficiency Index (EEI) calculated for refrigerators?
For refrigerators, the Energy Efficiency Index (EEI) compares the refrigerator’s actual annual energy consumption with the standard reference consumption calculated for that specific type and size of appliance.
Annual energy consumption is measured under standardized test conditions. For example, the standard reference consumption is calculated based on the refrigerator’s characteristics, including the volume and type of its compartments, and, of course, the food load.
For example, if a refrigerator consumes 200 kWh per year and its standard reference consumption is 250 kWh per year, the calculation would be as follows:
EEI = (200 / 250) × 100 = 80
The lower the EEI value, the more energy-efficient the refrigerator is according to the calculation method used.
For refrigerators, the EU energy label uses seven efficiency classes, from A to G:
| Energy efficiency class (refrigerator) | EEI |
|---|---|
| A | EEI ≤ 41 |
| B | 41 < EEI ≤ 51 |
| C | 51 < EEI ≤ 64 |
| D | 64 < EEI ≤ 80 |
| E | 80 < EEI ≤ 100 |
| F | 100 < EEI ≤ 125 |
| G | EEI > 125 |
Washing Machines
A separate method for calculating the energy efficiency index (EEI) is provided for washing machines.
In accordance with current EU regulations, the calculation is based on the “Eco 40–60” program. For machines that exceed the established small-capacity threshold, measurements are taken at various load levels and combined using weighting factors. The weighted energy consumption is then compared to the energy consumption of the standard cycle.
The current EU energy label for washing machines also uses the A–G scale.
| Energy efficiency class (Washing Machines) | EEI |
|---|---|
| A | EEI ≤ 52 |
| B | 52 < EEI ≤ 60 |
| C | 60 < EEI ≤ 69 |
| D | 69 < EEI ≤ 80 |
| E | 80 < EEI ≤ 91 |
| F | 91 < EEI ≤ 102 |
| G | EEI > 102 |
Dishwashers, EEI Index
There is also a standardized EU energy efficiency rating system for dishwashers.
As of March 1, 2021, the energy labels for dishwashers in the EU use classes ranging from A to G. The label is based on the “Eco” program and provides information on energy consumption per 100 cycles, water consumption per cycle, capacity, program duration, and noise level.
| Energy efficiency class (Dishwashers) | EEI |
|---|---|
| A | EEI ≤ 32 |
| B | 32 < EEI ≤ 38 |
| C | 38 < EEI ≤ 44 |
| D | 44 < EEI ≤ 50 |
| E | 50 < EEI ≤ 56 |
| F | 56 < EEI ≤ 62 |
| G | EEI > 62 |
Electronic displays and TVs
Electronic displays are another product category covered by EU regulations on energy labeling and ecodesign. The European Commission includes electronic displays among the regulated product groups.
It is calculated based on two main parameters:
P measured — the measured power consumption of the display when turned on, in watts;
A — the area of the visible part of the screen in dm².
The calculation takes screen area into account, so televisions of different sizes can be evaluated more accurately than by power consumption alone. Standardized test sequences are used to measure power consumption, with SDR and HDR considered separately
| Energy efficiency class (TV) | EEI |
|---|---|
| A | EEI < 0.30 |
| B | 0.30 ≤ EEI < 0.40 |
| C | 0.40 ≤ EEI < 0.50 |
| D | 0.50 ≤ EEI < 0.60 |
| E | 0.60 ≤ EEI < 0.75 |
| F | 0.75 ≤ EEI < 0.90 |
| G | EEI ≥ 0.90 |
