Water has a specific heat capacity of about 4.2 Kilojoules per kilogram per degree Kelvin, so it would take about 6 Kilowatt Hours of electricity to heat 100 Litres of water from 15 degrees centigrade to 65 degrees centigrade. As a standard immersion heater is 3KW, so it would take 2 hours to heat 100 Litres of water.
Drinking a large amount of carbonated drinks at bedtime can also cause hiccups, as the air in these drinks can distend the stomach. Consuming a large amount of alcohol before going to bed is another possible cause of hiccups during sleep. The excessive amount of alcohol can cause the stomach to distend.
1 doctor weighed in: What causes headaches during sleep? 1 doctor weighed in Want a second opinion? Could be a variety of causes- grinding your teeth in your sleep, what you might have eaten or activities during the day, neck posture on your pillow/pillows, Do you get headaches any other time? If this is repetitive, see a Dr. and hopefully determine the triggers. Would you like to video or text chat with me?