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We’re all familiar with incandescent lights. They’re a very, very mature technology: highly standardized sizes, with known expectations for light output of different wattage bulbs. We all have an intuitive idea of how much light a 60W bulb puts out, right? But if we’re buying LED bulbs, we need to become acquainted with the light output measurement that lighting designers and engineers use to compare lights. Light intensity is measured in lumens (lm). Here are some useful figures for good ole incandescent bulbs:

Watts	Bulb Type	Lumens
60W	A19/E26/E12	800 lm
100W	A19/E26	1600 lm
65W	BR30	620 lm
75W	PAR30	1100 lm
10W	halogen	80 – 150 lm
20W	halogen	170 – 250 lm
50W	halogen	400 – 550 lm

You’ll find the lumen rating on the packaging of most bulbs and included in product descriptions on websites. If they don’t tell you how many lumens and just say something like “75W equivalent”, beware! A lot of product descriptions on sites like Amazon or Home Depot are tweaked to make LED bulbs seem brighter than they actually are, by equating them to wattage equivalents for incandescent bulbs. But lumens don’t lie – a 400 lm MR16 halogen bulb at 50W is just about the same brightness as a 435 lm LED MR16 replacement bulb at 7.5W, but the LED is 6.6x as efficient.

A common way to express efficiency is in lumens/watt. California, defying the Trump Administration’s DOE who are eager to gut efficiency mandates from earlier administrations including G.W. Bush and Obama, requires most bulbs sold in California to deliver at least 45 lm / watt efficiency. Nearly everything you’ll find in standard bulb replacements meets this requirement. That LED bulb example above is 58 lm / watt. The halogen is just 8 lm / watt.

While efficiency is important, if you sacrifice other characteristics you want for maximum efficiency, you’ll be saving the planet a tiny bit better, but you’ll hate your lights. All LEDs are efficient, so don’t stress too much about it. Stress a lot more about the other stuff I will tell you about in later posts!