No surge, but a big steady draw
A space heater has no motor, so its starting watts equal its running watts. But 1,500 W is a lot to run for hours on a small generator, and it burns fuel quickly.
If you have a gas furnace, running its blower usually heats the house for less power than space heaters.
Getting more warmth from less generator
Heat is the most expensive thing to make with a generator. A space heater turns every watt into heat, so it draws about as much as a microwave — but for hours instead of minutes, and it burns fuel steadily the whole time.
Heat one room instead of the house: close the doors, hang a blanket over an open doorway and keep everyone in the warm room. If you have a gas furnace, its blower usually needs less generator power than space heaters and warms every room.
Never heat the house with a gas oven or stovetop[1], and never bring the generator inside or into a garage.[2]
Questions
Is it safe to use a space heater on a generator?
Space heaters should plug directly into a wall outlet, not an extension cord or power strip[3] — so on generator power the safest setup is a transfer switch feeding your home’s outlets.[4] Keep the heater at least 3 feet from anything that can burn[5] and the generator outdoors.[2]
Oil-filled radiator or ceramic heater?
At the same setting they draw about the same power — an electric heater’s output depends on its watts, not its type. An oil-filled radiator stays warm longer after it cycles off, which smooths out the load a little.
Can a small inverter generator run a space heater?
Usually only on its own. A space heater takes most of a small inverter’s capacity, leaving room for little more than phone chargers and a light. Mark it “can take turns” in the calculator to see what else fits alongside it.