Energy efficiency defines the use that electrical appliances make of the energy they receive.
In the case of the lamp, the smaller the amount of energy dissipated, the greater its energy efficiency, as this means that most of the energy supplied was well used and there were few losses. The same happens with all other devices that need a source of energy to work. Thus, energy efficiency (represented by the letter e ) is defined as the ratio between the amount of energy used during the performance of some activity and the energy supplied.
This relationship can be mathematically described as:
e = E used
The closer to 1 the value assumed by e, the greater the energy efficiency of the appliance. But the closer to 0, the lower the energy efficiency.
Estimating energy efficiency has become fundamental nowadays, since it allows us to define whether or not energy is being used well by the appliances used in our daily lives. Furthermore, the development of science has allowed the construction of devices that make the best use of the energy supplied to them.
In order to encourage the manufacture and purchase of more efficient products, the PROCEL energy saving seal was created in 1993, which indicates to the consumer, at the time of purchase, the products that present the best levels of energy efficiency.
This seal consists of a scale of letters from A to E, as shown in the figure at the top of the page. Appliances that receive an A grade are the most efficient, while those that receive an E grade are the least economical. Therefore, the recommended way to reduce energy consumption is to always buy appliances that receive grade A.