Anyone using their DRLs?

I used the regular headlights almost fulltime in daytime on my first Prius, and on the car before that. The 2012 is my first with DRLs of any sort, and I'm a convert. Past calculations suggested that full head/tail/side lights should cost something under 1 mpg at highway speed, maybe up to 2-ish in city traffic. The LEDs should slash that by a factor of 10. I'll take that.

With a non-PiP, I don't have real LEDs in the headlight assembly, only LED-like decorations.

 

1-2 MPG because of headlight usage?! No way... I find that hard to believe.

Nexus 4 ? 2

 

mine are on at all times with the position light too....primarily thinking in safety

 

I don't think I understand how using an LED or any light would affect mpg. Do you guys really see a loss?
I run my DRL's all the time, with the parking lamps if its cloudy and headlights if its rainy or obviously dark. I also run my upgraded stereo, amps, and subwoofer for 200 miles a day and I see no change in mpg from the days it was new. Are you sitting in bumper to bumper traffic a lot?

 

In Canada, DRL is required to be on by law. My Odessey do not have the option to turn it off. LED DRLs draw very little electricity and have very long lifespan.

 

I've always had DRL but these are my first LED. I like them but I hate that Toyota put them so low on the Prius.

 

I keep them on all the time- with no MPG hit- there's no reason not to use them.

 

I don't notice a loss because it is small and I've never tried to measure that specific item. But others have analyzed it more carefully.

Lights consume energy. Under the laws of physics, this has to come from somewhere. In a car, unless it can be harvested from a waste stream, it must come out of the MPG.

[Warning -- generic round numbers ahead, not accurate measurements with detailed calculations]

Traditional lights (headlights plus everything else that comes on with them, e.g. taillights, front and side marker lights, increased dashboard lights) are typically in the vicinity of 200 watts. (Prii with LED taillights should be somewhat less.) For a car consuming 250-300 Wh per mile while getting 60 mpg at 60 mph, this costs somewhere between 0.5 and 1.0 mpg.

For a car going slower, with much waiting time at stoplights, the ratio changes. The lighting energy load doesn't stop while the car sits still. A car progressing on city streets at an average pace of 30 mph, consuming under 200 Wh/mile and getting over 70 mpg, will lose more than 2 mpg to the headlights.

Traditional DRLs, in the form of reduced voltage headlights, consume 40-ish watts (as remembered from some past energy study.) Just looking at the LED DRLs, my engineering swag is no more than 20-ish watts for the pair, someone else claimed 8 watts. This is roughly a 10X (from my swag, more from the other number) reduction in parasitic load.

 

There can not be a measurable loss. I don't even notice a difference on my commute at night running the Seat heaters on High for the entire 11 EV miles of my 14 mile drive. Seat heaters and headlights or no heaters and no lights still causes me to drop EV at the exact same point between to lights about 500 yards apart. I'll attest that 500 yard varience to a combination of lights synching and human driving not being perfectly repeatable.

 

There has to be a loss, it is required by the first law of thermodynamics. Whether or nor you can measure it is another matter.

You are measuring to 500 yards over 11 miles, a resolution of 2.6%. At highway speed, I'm looking for a difference barely over 1%.

 

Our DRL's are the (non-LED) high beams, on at reduced brightness. Any time the car's on and headlights off, that's the configuration. Turn the head lights on and the DRL function cut's out.

 

Not sure if this is what the original poster was looking for, but here goes:
I use headlights if I have trouble seeing without them (namely, at night).
I use DRLs when I can see fine, but think that others might have trouble seeing me (during foggy days, rainy days, when I'm going in-and-out-of tunnels).

(An interesting legal question: in a state like NJ where headlights have to be on when it's raining, do DRLs satisfy the legal requirement, or can you be ticketed if your DRLs and not your headlights are on? I don't think they count.)

 

Do not satisfy the legal requirements, in NY State it's mandatory when you have your whippers on to have your HEADLIGHT ON.
DRL are not a sufficient source of prevention for a moving vehicle for this type of conditions without the side markers.

 

I use my DRL's always. If not my headlights are on. better more light than not!

 

Wipers On Headlights On...or Wipers On Lights On? - Hackettstown NJ

 

Here is a better breakdown. Let's say the lights are 200 watts. You are driving at 30 mph, in EV mode and using 200 watt-hours per mile. In 6 minutes you will go 3 miles and consume 600 watt-hours to drive. In the same 6 minutes (1/10 of an hour) the 200 watts from the lights will consume 20 watt-hours. This is a 3.3% penalty. This is probably hard to measure, since you can easily vary on a single trip by +/- 5%. But consider that you might be driving 30 mph, but spending 1/3 or 1/2 of your time waiting at stop lights...averaging only 15 or 20 mph. Now the penalty is as high as 6.6%. Both seat heaters, lights and wipers could be as much as 10%, especially in stop and go traffic.

Moving on to gas mpg. At 50 mpg the gas engine is consuming about 3x as many BTUs per mile (with about 2/3rds going to waste heat). This makes the penalty for the lights drop to about 1.1% (at 30 mph).

Mike

 

every day. its bright enough to get attention and maybe prevent an error from another driver. just one more safety tool in the tool box of life (wow pretty deep).no tkts no accidents for 55years.there are just little things that help prevent accidents aside from dont drive drunk etc. the main thing i learned at age 17 was (and is) drive with the" what if" thought. ie what if this guy slams on his brakes. what if this guy runs a stop sign. the other major thing i learned was drop back one car length for every 10mph you are driving. and make sure others see you. geesh, whats with me going off on my soap box. ps. always go with the flow of traffic. if the group is under speed limit you go under speed limit. if all the traffic around you is going 70 in a 55, you go 70 in the 55. never enter a highway beside another vehicle be a little ahead or a little behind. ETC ETC ETC . okay i think im thru running my mouth for now. sorry.

 

I start to part company, with that "70 in a 50" credo. It's inflationary when everyone follows that: speeds keep going up and up.

I prefer to hunker down behind a slow truck in the right lane. And if there's none to be found, I'll volunteer.

I also increase following distance a bit beyond the guidelines, has several benefits.