how do I determine which heater is more efficient?

[YamatoTwinkie]

@CC

That’s pretty much my calculations. And the furnace doesn’t run for an hour straight. It runs for a few minutes and then cuts off for several minutes. So it seems to me that there’s a balance point where letting the furnace heat the house costs as much as letting the heater heat the room.

Yes, there’s a balance point, if your numbers are correct.

They’re not.

[YamatoTwinkie]

@Santo_Rugger

Also, am I thinking wonky, or is 3kW really small for a whole house (or single apartment apartment) heater? That’s only about 10,000 BTU (per hour)

Yeah, this site recommends an electric furnace sized to 25Btus/sqft for moderate climates. For a 3kW heater, that works out to 408 square feet.

[Santo_Rugger]

@YamatoTwinkie

Yeah, this site recommends an electric furnace sized to 25Btus/sqft for moderate climates. For a 3kW heater, that works out to 408 square feet.

And the OP seems to have at least two closed rooms (which presumably means there are two open rooms). It sounds like it’s undersized, to me.

Can I ask where you live, CC? Or at least the expected average low in December/January?