[Big Kev-O]

Originally Posted by Accelo

The old style round headlights were typically 55/65 watts.
The low beams pulled 55 watts. The high beams pulled 65.
With the two low beams on the car pulls 110 watts combined.
(110 watts divided by 12 volts gives you 9 amps).
Add in the high beam at 130 watts combined and you're sucking down about 11 amps.
All four headlights on will draw 20 amps.

Accelo is spot on with this information. You need two relays to operate low & high beams. If you use a single fuse for both relays 25A or 30A would be sufficient since your load should not exceed 80% of the fuse rating.