Electricity is generated from the burning of coal, petroleum and natural gas that are regarded as non-renewable resources. These resources cannot be replenished in meaningful human timeframes once being consumed. As a result, energy crisis may arise if electricity is not consumed sustainably. Efficient energy use is a concept to conserve energy by reducing the amount of energy required for provision of products and services. Energy efficiency can be generally improved by adoption of a more efficient production process or technology such as the installation of LED lightings. Besides, increasing energy efficiency can also reduce the greenhouse gas emissions caused by the combustion of fossil fuels. This may help mitigating the problem of climate change.