I have two gas fireplaces, neither use power (nor have any available). Valves and safety is handled via millivolt thermopiles in the pilot light and main flame. Heating happens via convection through ducts that run from below to around/behind the fireplace itself, then out over the top. It passively moves a fair amount of air and can make the room uncomfortably warm if left on too long.

I have no idea if this is common or not, but I know of at least two counterexamples to your statement here in Michigan.

> Yes, they do need need electricity.

Some do, some don't. Mine has a pilot light and a thermocouple. I used it to keep warm while our power was out for three days this past weekend.

I wouldn't be surprised if pilot lights aren't illegal now. They're terribly inefficient, more so if your furnace rarely lights.

I think pilot lights are still pretty much standard on certain appliances, like water heaters and fireplaces. Probably deliberately so they can run without power. All my other gas appliances are electronic ignition, e.g. we have to use a lighter to start the range when the power is out.

In the case of gas fireplaces, all of the heat generated is used, so I would think it would be perfectly efficient. As long as you shut it off during the warm seasons, anyway.

What's the make/model? Presumably not forced air?

The house I live in has two gas fireplaces, both 20-30 years old. They work in the same manner described above, with no requirement for electricity. Each one also has a blower that is simply plugged into the wall (one runs continuously, the other is thermostatically controlled; both are very loud). The blowers are optional, and the house gets adequately heated even when they are off.

Not sure about make & model, I'd have to find the paperwork from when the house was built 8 years ago. It's radiant, not forced air. That's an option I could add but it would require electricity for that part.

GP said fireplace, you're talking about furnaces. Plenty of fireplaces don't need power, but I've never seen a forced air furnace without power, and I don't think it's possible.

Gas fireplaces generally do not require electricity and many have no fans. Exhaust is passive, and thermostats use a thermopile that generates a small current from the heat of the pilot light. The pilot light is started manually with a piezoelectric starter, or a lighter.

Gas fireplaces are slightly less efficient than high-efficiency furnaces because some heat goes out the exhaust.