Naphthalene has a calorific value of 41.9 MJ/kg, which means that one kilogram of naphthalene can produce 41.9 mega joules of thermal energy when burned. This value is relatively high compared to other fuels, such as coal, which has a calorific value of 29.3 MJ/kg, and natural gas, which has a calorific value of 38.9 MJ/kg. This makes naphthalene a particularly attractive fuel for industrial and residential heating applications.