From regular to LED bulbs – How much of a power savings can you expect?

It’s a well known fact that LED’s require very little power to provide the light of a similar incandescent bulb. In automotive applications, there are situations where reducing the power draw is desired. Switching to LED’s can be helpful here.

In this test, I replaced the “parking lights” in a vehicle with LED’s. “Parking Lights” refer to all the lights that are on when the headlights are on (with the exception of the headlights themselves).

In this case, it included:

  • Front Side-Marker Lights x 2 (194-type bulb)
  • Rear Side-Marker Lights x 2 (194-type bulb)
  • Rear Park Lights x 2 (1157-type bulb)

Replacement bulbs were ordered as follows:

  • 2 x 194 Yellow (4-bulb LED)
  • 2 x 194 Red (4-bulb LED)
  • 2 x 1157 Red (24-bulb LED)

With an ammeter, I measured the current running through each bulb. Here are the results:

Regular BulbLED
194 bulb0.25A0.04-0.05A
1157 bulb0.57A0.04
Total current with all bulbs2.14A0.24-0.28A

As you can see, over 2 amps is pulled by the regular bulbs. Less than 1/8 of that power draw is pulled by the LED’s. Even more shocking is the actual brake circuit of the 1157 bulbs (not listed in the table). Each bulb pulls 2.08A when braking, while the LED’s pull 0.12A. In this case, the regular bulb pulls 17 times as much current as the LED. In all fairness, the 24-bulb 1157 LED’s aren’t quite as bright as the regular bulbs. A 30-bulb 1157 LED would be much more similar, and would probably pull only a tiny bit more current.

Certainly, by replacing regular automotive bulbs with their LED versions, you can reduce the current draw, and help to reduce the load on the alternator (or reduce the current drawn from the batter when you’re running without an alternator). Based on the information I’ve been able to collect, it would seem that the reduction can be anywhere from 1/8 to better than 1/16 of the current draw.