Turning a kilogram of boiling water into steam takes 2,256 kJ, about 5.4 times the 418 kJ it takes to heat it from 0 to 100 °C.
Heating only speeds the molecules up. Boiling pulls them apart against the attraction that holds a liquid together, with no rise in temperature, and for water that attraction is strong. So a pan left on the heat takes five to seven times as long to boil dry as it took to come to the boil, and melting ice takes 334 kJ, as much as warming the same water by 80 °C.
The 2,256 kJ is at 100 °C and normal pressure. At room temperature a kilogram of water evaporates for about 2,440 kJ, and at the lower boiling point on a mountain it takes a little more. The rule is for water; other liquids have much smaller latent heats (ethanol, 841 kJ).
Estimate with the rule, then check it against the calculator that models it properly.
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