Gas stoves with pilot lights

Or that they wanted some good margin, so that the flame is still enough with an aging thermocouple, that it's harder for the wind to blow out, etc.

If you turned off the furnace in the summer, it

I used to turn off the pilot on my old furnace. Never thought about the fact that with a water heater the pilot helps heat the tank a bit.

So I just did the promised pilot light usage test for my water heater here. It's just a basic State water heater with pilot light, about ten years old. I stopped it from firing and turned the thermostat down so the furnace wasn't running. In two hours it used 0.6 cubic feet. That's 7.2 cubic feet a day, 216 a month. Applying current gas rate, it's $2.50 for the gas. That excludes the monthly gas base connection fee of $10. Depends on what you want to do with that, ie divide it up between furnace, WH, and gas grill or ignore it, because that charge would be there for just the furnace anyway. If you only had a WH the full cost including the entire $10 would be $6. If you average the $2.50 and the $6, it's in the range of Ed's numbers.

Even at the $2.50 monthly cost, that's $30 a year, $300 over ten years. It does add up and you would likely recover the cost of a better model with electric ignition. while also reducing CO2. Also not taken into account is any heating effect the pilot light might or might not have. I think it's even possible the pilot light makes it worse, because it pulls more air in and moves it through the tank than not having it there would. And the power vent ones with electric ignition are going to be a lot better there, they close off the flu when not firing.