The first type of heating system that didn't require manual stoking was fueled by _________.

The first type of heating system that didn't require manual stoking was fueled by oil. This is because oil heating systems, particularly those that utilize oil burners, are designed to automatically draw in and burn fuel oil without the need for manual input from the user. These systems typically use a pump to supply oil to the burner and are equipped with controls that regulate the operation based on the desired temperature. This automation provides convenience and efficiency, eliminating the labor-intensive process of stoking required in older coal-fired systems.

While coal, gas, and solar energy systems have their own methods of operation, they often involve more manual intervention or complexities compared to oil heating systems. For example, coal heating required frequent manual feeding of the furnace, whereas gas heating systems can be more efficient but often still depend on manual ignition in traditional setups. Solar energy systems, while increasingly popular, do not provide the direct heating capabilities that oil systems do in many climates and require supplementary systems to function effectively during less sunny periods.