Every light bulb is essentially a tiny, contained heater. Incandescent bulbs, those old-school glass orbs, convert only about 10% of their energy into light—the rest is wasted as heat. That means a 60-watt incandescent bulb is kicking out roughly as much heat as a small space heater running on low.
LEDs, on the other hand, are the cool kids of the lighting world. They convert about 90% of their energy into light, leaving only a measly 10% as heat. So if you’re running a string of modern LEDs, you’d need a lot of them to feel a difference—like a hundred bulbs all glowing at once.
Even then, the heat from LEDs is negligible in a well-insulated room. To truly raise your thermostat by a single degree, you’d need to fill an entire room with incandescent bulbs, turning your living room into a miniature film set from the 1950s.
