You have electric heat for the entire house? That's an unusual setup - most places with electric heat have a separate thermostat in each room.

To do the whole house means you have air vents to the entire house, with a central electric heat source? I guess maybe that makes sense if you anyway have central A/C? I don't think that's common in Canada though.

You're thinking of resistive electric heat, a baseboard-style system.

But in many areas an electric heat pump is common. This is a forced-air system, and controlled by zoned thermostats just like traditional gas or oil heat.

That said, such heat pumps actually have multiple states:

* Cooling

* Off

* Heating

* Emergency heat (aka Aux heat)

That last one happens when the ambient temperature is so low that the heat pump can't scavenge enough heat, and needs to augment with resistive heat (which happens through the same forced air delivery). Thus, in extreme cold you may be using even more electricity than you normally would.

I live near Austin. The only time I've seen the Aux Heat in use was during last year's February freeze, which at 6F was the lowest temperature ever recorded here. Even at the occasional 13F-15F temperatures, the heat pump still operates normally (albeit it at very long cycles).

Most heating heat pumps I've seen can ramp up/down as demand changes.

Also central heat pumps (for heating) aren't so common, most are mini-split types with each room separate, or at least a highly variable central compressor than can run on low.

I don't have any factual citations, but I suspect they're a lot more common than you think. At the very least, they're completely ubiquitous in central Texas. I'd imagine that's a combination of temperate conditions (as opposed to Minnesota, it never gets to the 6F temperature here), and newer construction (older houses are probably less likely to have a heat pump anyway, but with the insane growth in real estate around here, there's not very many old houses).

Most heat pumps these days are mini-splits, not ducted. And they have a separate unit in each room. Either with multiple compressors outside, or a single one that can ramp up/down.

Heat pumps are useless in hard frost.

The one I own stops being useful at 3 degrees of frost, struggles before then

As I wrote above, the only time I've seen mine falter was at 6F (last year's mega freeze in Austin). It occasionally gets to 13F-15F in the winter, and the heat pump works in this environment without having to resort to "aux heat". I'm sure it's become rather inefficient, but it does work.