Okay, here’s my unscientific, real-world breakdown (tested via personal shivering):
— Naked on a cold sheet: 45 minutes to 1 hour. (You’re a heat traitor.)
— Under a duvet with you: 2 to 3 hours. (Acceptable.)
— Wrapped in fleece, inside a sleeping bag: 4 to 5 hours. (This is peak performance.)
How Long Does a Hot Water Bottle Stay Hot? Essential Insights Revealed
If you want it to last all night, preheat the bed by placing the bottle in the spot where your feet will go 20 minutes before you get in. By the time you slip in, the mattress is warm, and the bottle still has juice left. It’s like having a secret heater without the electricity bill.
