I measured current draw for the Sylvania ECO HB2 bulbs I put in my Civic.
Sylvania 9003/HB2/H4 EB EcoBright Headlight Bulb (Low/High Beam), (Pack of 2) : Amazon.com : Automotive
Funny, I don't seem to have written it down, but I remember thinking, "so it's actually 25% lower power than stock."
BUT, that was only for the low beam. For high beam, they were exactly the same.
I wish I could put HID or LED in there for some much larger power draw reduction, but alas, headlamp reflectors are designed for a very specific source geometry, as of now there isn't a way I know of to make the swap without changing the entire assembly.
The ECO headlamps still rank as the cheapest way to knock out ~20W, although I find swapping headlamps to be a surprising PITA. I'm still trying to find good LED's for the tail-lamps, so far I've had no luck finding 1157 LED bulbs that actually work in the Civic's sockets, at least not under $10/pair.