many will say that headlights being on is a minimal impact to mileage... but its still an impact. in cities, DRL's are nearly completely unnoticed by me. so i keep them off until dark, i use running lights only during the fading light...when i have a chance. being this far north, its dark coming and going to work and would be even if i were only doing 8 hour shifts i will say that in the Mojave Desert, in bright sunlight on one of those 10 mile straightaways, i could see it as being a safety issue, but no where else really
Assuming 20 amps for the headlights, that's a 240-watt load at 12v. That 240 watts is about 0.33 horsepower. Even allowing for conversion inefficiency, it's below one horsepower. I don't use my HID headlights except at night, but I'd like some type of DRL. There have been several times where, after a quick glance, I didn't immediately spot a silver/gray car on a concrete road. If he had DRLs, that would have made all the difference. I worked out a scheme to rewire the Prius fog lights as DRLs, retaining the same auto-off as the headlights. But I never got around to implementing it.
I can't actually answer the poll, as my answer is "At night, when it's raining, when it's really cloudy, or foggy, or if I notice that I'm not seeing other cars really clearly"... basically, they aren't on if the sun is on full bright, and they are on otherwise.
All the time. Last two cars (96 Grand-Am and now '07 TCH) have had DRL and Auto-Lights. I think I have always run with lights on. Like Galaxee, mine are halogens and normally last a LONG time and relatively cheap.
In Canada, we have DRLs and they're about 80% full intensity so they're "on" all the time. I have the parking lights on any time it's gloomy (not necessarily cloudy since it can be cloudy and still fairly bright), misty, raining etc (basically the "bad weather" part in the poll). I also have them on if it's sunny in the winter (because of the low sun angle). I'll use full headlights if necessary (heavy rain/snow, fog, night of course). DRLs may not be useful down south but when the sun's at a really acute angle (or a large angle if you're using azimuth), then having the lights on really help me see the oncoming cars against the sunlit background.
Mine are always on. It's not so much the safety of having them on in fair weather, but like auricchio said, I want to make sure my Tideland is visible against the background and especially at dusk. These days, it's dark when I'm going to work and dark when I head home.
I have mine on all the time. bulbs and ballasts are not that expensive and if it can even remotely reduce the risk of an accident then I will use them. On most days I always notice the car with it's headlights on faster than I do then if he had them off. It is really pronounced when near parked cars as it immediately lets you know that car is on and may be moving.
What is the cost of replacing the HID lights? I wonder if they will need to be replaced at an earlier age if they are on all the time.
HIDs aren't cheap (~$300/bulb) and the only instances DH ever saw of HIDs burning out were full time use. and that was only a couple of them.
I read it somewhere that turning on the headlights during daytime is actually a very cheap insurance. It makes sense but I still don't do it.
Dealership prices for the bulbs would indeed be expensive. I would simply replace mine with aftermarket units. They can be had for $150-$400 for a complete set including ballasts. Difference in price being asian equipment vs german equipment usually. I've used the cheaper aftermarket units on two of my trucks and my Trans Am and they worked well. One did have an issue with not turning one of the bulbs on reliably though. That's what I get for going cheap!
This seems like a no-brainer to me. I leave them on all the time. For a very small increase in energy, I get improved safety, and the convenience of not having to touch the light switch (since the lights go off automatically when I turn the car off and open the door).