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.
A large number of medications may cause hiccups. Medications taken only at bedtime, such as sleep medicine, cause hiccups primarily during sleep. Other medications cause hiccups at other times of the day as well. These are examples of medications that may produce hiccups: Sleep medications: eszopiclone (Lunesta)
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?