The oil inside an electric heating oil heater is typically fuel oil, also known as heating oil or kerosene. Fuel oil is a type of petroleum distillate that is used for heating purposes in residential and commercial buildings. It is chosen for its high energy content and ability to burn efficiently in electric heating systems.

Fuel oil is preferred in electric heating oil heaters due to several reasons. Firstly, it has a high energy density, meaning it contains a significant amount of energy per unit volume. This high energy content ensures that the heater can produce a substantial amount of heat, making it suitable for colder climates. According to the U.S. Energy Information Administration (EIA), the energy content of fuel oil is approximately 138,690 British Thermal Units (BTUs) per gallon, which is higher than many other types of heating fuels.

Secondly, fuel oil is readily available and widely used in the United States. It is commonly stored in tanks on-site, which simplifies the refueling process. The availability of fuel oil makes it a convenient choice for heating systems, especially in areas where natural gas or electricity may not be as accessible.

Furthermore, electric heating oil heaters are designed to burn fuel oil efficiently, minimizing waste and emissions. Modern heating systems incorporate advanced burners and controls that optimize the combustion process, resulting in higher energy efficiency and reduced environmental impact. According to the EIA, the average residential heating oil consumption in the United States was approximately 1.1 million barrels per day in 2020.

In conclusion, the oil inside an electric heating oil heater is typically fuel oil due to its high energy content, availability, and efficiency in heating systems. The use of fuel oil ensures effective and reliable heating, particularly in regions where other heating options may be limited.