09/17/2026
For its first thirty years this thing was hospital equipment, and it ran like it.
Before antibiotics, the standard treatment for tuberculosis was cold fresh air, so sanatorium patients slept on open porches through the winter and sometimes woke with frost on the covers. The heated under-blanket, credited to the American physician Sidney I. Russell around 1912, existed so those patients could stay warm from below while the freezing air above them did its supposed work. It was never sold as comfort, and for decades it was priced, stocked, and maintained like the ward equipment it was, well out of reach of an ordinary household budget.
Those early versions had no thermostat at all, so the element ran at full rated power from lights out until morning. A 150-watt pad with no cycling burns 1.5 kilowatt-hours over a ten-hour night, while a modern thermostatic blanket averaging 30 watts uses 0.3 kilowatt-hours across the same night. That is five times the energy for a heat that was less even, far harder to sleep under, and impossible to turn down without getting out of bed.
The fix arrived in 1936, when the first thermostatically controlled electric overblankets reached the market and the element finally learned to switch itself off. The war pushed the technology hard after that, because American bomber crews flew in electrically heated suits at altitudes where the temperature hit 50 degrees below zero. Those crews came home in 1946 to the first mass-market automatic electric blankets, built on wiring and controls that had already been proven at 25,000 feet.
The cost picture flipped completely along the way. What started as specialist ward equipment now sells for $30 to $60 and runs on pocket change, and the thermostat is the entire reason, since it turned an appliance that consumed power all night into one that spends most of the night switched off and coasting on heat it already made. One habit still carries over from the sanatorium version worth copying: put the heat underneath you the way the original was designed, so warmth travels up into the mattress and into you instead of drifting off the top into a cold room. [KH064]
