Before you go out and buy an electric heater, be aware …

1) All electric heaters are 100% efficient — wasted energy becomes heat in an electric heater, which is useful heat.
2) All 120 volt electric heaters that plug into the wall are 1,500 watts or 12.5 amps or 5,115 BTU.
3) Occasionally, you’ll see less then 5,000 BTU electric heaters, but they are rare, as electric coils are cheap to make, and you want to heat the room as quickly as possible — 5,000 BTU is less heat then you think.
4) The maximum electricity you can safely pull from a 20 amp circuit constantly is 12.5 amps. Run any more then 12.5 amps through such a circuit constantly, your wiring may start a fire. The breaker is rated for 20 amps to provide enough current for induction current for starting electric motors.
5) Don’t plug anything but a electric heater in a 20 amp outlet at any one time.
6) Electricity is expensive, because electricity generating plants aren’t that energy efficient — the laws of thermodynamics keep coal and gas plants between 25-35% energy efficient at generating electricity. In contrast, a household gas furnace might be 95% energy efficient. It’s a lot more efficient to directly burn coal or gas to make heat then electricity.
7) Electric heaters with oil heat up slower and cool down slower. They don’t save energy, they just stretch out the time the unit is warm. A cheap 1,500 watt fan heater is going to be just as warm as an expensive unit with oil, but the prior will heat up faster and cool down faster.

Additional fun facts about pumping versus generating heat that Greenies want you to know:

A) Air source heat pumps (e.g. split unit air conditioners run backwards) are 250% efficient at pumping heat compared generating heat directly. As you are moving heat not creating it, takes less energy move it around then actually create it. A 250% energy efficient heat pump x 35% efficient coal electric power plant = 87.5% energy efficiency in heating = older oil burner in a house.

B) Ground source heat pumps (e.g. the misnomer I hate geothermal) are 400% efficient at pumping heat. That’s because the temperature in the ground is usually much closer to your desired temperature in the building in most climates — so less compression of the coolant to pump the heat compared to air-source heat pumps. Take that same 35% efficient coal electric power plant and heat your house with a ground source heat pump that is 400% efficient and you’ll reach total 140% energy efficiency — more efficient then even a natural gas burner in your house, directly burning the fuel.

This is my Big Buddy Heater in 18,000 BTU mode — aka 5,275 watt output.