is there a formula to compare HID lighting to LED to get the visible lumens?

The rule of thumb for currently available white LED lamps in service is about 60 lumens/watt.  But, developers are coming up with more and more efficient LEDs almost every month (Cree has the current record at over 200 lumens per Watt -- but these won't be available in plug-in headlamp replacements for several more years).  There are commercially available white LEDs that are good for over 100 lumens per Watt that might make their way into auto headlamps within a year or so.

HID "burner" type lamps are good for between 80 and 90 lumens per watt.

So.... right now, HIDs are a little more efficient than LEDs but that will change in the next year, or two.

Even so, LEDs last much longer than HIDs.

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