Electronics, Lighting, & Gadgets - lumens and watts

The P-7 in high mode throws off 900 lumens as output. How is that comparable to say a brand new incandescent light bulb expressed in wattage? In other words, when I go to buy a replacement incandescent light bulb, its stated in terms of watts. But how much lumens on a brand new bulb?

Lumens and watts are two completely different measurements that have absolutely nothing to do with each other.

Most incandesant bulbs will have their lumen output listed on the packaging, but since most people are used to referring to wattage (which is a measurement of heat and is actually energy wasted) that is what is printed in big letters.

Also, light output from LEDs is generally measured in candela, not lumens.

You are trying to compare apples and oranges.

The Watt rating of a bulb is the power consumed, not the amount of light put out.

Lumens is a measured light output.

They aren't really directly comparable.

since most people are used to referring to wattage (which is a measurement of heat and is actually energy wasted) that is what is printed in big letters.

Wattage is power consumed, Power equaling Volts x Amps and is not a measurement of heat.

However an incandescent bulb is so inefficient that it does mostly output heat.

eg. a 60W bulb might produce 55W of heat and 5W of light.

The P7 lumen count is more like 500-700, depending on the model.

As a rough guide, a typical setup LEDs will run 2-4x the lumens of the same wattage halogen, sometimes better, sometimes worse.

A cheap P7 light will likely give a somewhat comparable riding experience to a 20W halogen... ie sufficient for pretty much all road riding, though you might want two for MTB.
I hope this is suitably vague to avoid the flames.

A 60 watt bulb puts out 825 lumens according to the GE spec.

http://en.wikipedia.org/wiki/Luminous_efficacy#Examples_2