I think the EM Wiki needs to be updated on LEDs (ref post #10).
1. Differentiate halogen head-lamps vs parking/tail-lights.
2. Explain geometry problem with swapping halogen low-beams.
3. Define motivation for power reduction.
4. Include HID discussion.
5. Remove obfuscating references.
Now... back to 'eco' halogens? (End thread-jack?)
They reduce power in the low-beam setting, but not a ton, 20W total in my test, and unlike LEDs and HIDs they are halogens with the proper geometry so the low beam pattern meets DOT approval (and is socially responsible).