Which of the following is NOT a feature of electric heaters?

Electric heaters are known for their efficiency in converting electrical energy into heat, which means they typically have high efficiency ratings. They often require minimal maintenance compared to other heating systems because they have fewer mechanical parts that can wear out over time. Additionally, electric heaters provide immediate heating, allowing rooms to warm up quickly once activated.

The use of fossil fuels is not associated with electric heaters since they operate purely on electricity. This differentiates them from other heating systems, such as gas or oil heaters, that rely on fossil fuels for their operation. Therefore, the correct answer reflects that the use of fossil fuels is not a feature of electric heaters, highlighting their unique characteristic of relying solely on electrical power for heating.