We are witnessing a revolution. Not the political revolution creeping across the Arab world. Not the information revolution playing out in Silicon Valley. A light bulb revolution.

Think about it. Thomas Edison and English inventor Sir Joseph Swan independently produced the first reliable, affordable incandescent bulbs around 1880, and the invention dominated the home lighting industry for around 130 years. That’s longer than steam-powered locomotives dominated American rails. Longer even than Edison’s other great household invention, the phonograph, ruled the recording industry. But 30 or so years after the phonograph faded, the incandescent bulb now seems to be on its way out as well.

The problem is that the design of the standard incandescent bulb is hopelessly inefficient.

Electricity heats up the atoms in the filament, exciting electrons that release light. In the end, only 10 percent of the electricity that runs through the bulb actually generates light, with the rest used to heat the filament to more than 4,000 degrees.

In 2007, President George W. Bush signed the Energy Independence and Security Act, which annually increases efficiency requirements for light bulbs. By 2020, screw-in light bulbs will have to be 60 to 70 percent more efficient than today’s incandescent bulbs.

While the law doesn’t explicitly ban incandescent bulbs, they effectively have one foot in the grave. Manufacturers phased out old-style 100-watt incandescent bulbs as of Jan. 1; in many places only a few remain on retailers’ shelves. New types of incandescent bulbs comply with this year’s modest efficiency requirements, but it’s not clear that the design can ever meet the 2020 standards.

As we move away from standard incandescents, however, it’s not entirely clear what we’re moving toward. Several designs — including compact fluorescents (CFLs) and light-emitting diodes (LEDs) — meet the federal standards. So which of these is best for the environment?

The government has given you a little help in the form of a label. As of this year, bulb packages list lumens (how much light the bulb produces), watts (the power required to produce it), expected life span and a brief description of the light (from “warm” to “cool,” whatever that means).

If you were interested only in your personal energy bill, these labels do the job. But there’s much more to assessing a product’s environmental impact than counting up the kilowatt-hours it consumes while in use. It takes resources to mine the raw materials, assemble the product, transport it and dispose of it.

This was, in fact, the primary argument against compact fluorescent bulbs a few years ago. CFLs are the coiled tubular bulbs that you probably picture when you think of efficient bulbs. An electric current excites mercury and argon vapor inside the tubes, prompting the atoms to release ultraviolet light.

Assessing CFLs

Critics of CFLs argued for years that, while the newfangled bulbs consumed less energy during use, their manufacture was so complex and exacting that they had a greater environmental impact over their lifetime than incandescent bulbs. (Virtually all new products marketed as environmentally friendly face this charge at some point, justifiably so in some cases more than others. Consider, for example, the preposterous Internet-sustained assertion that Hummers are actually better for the environment than hybrid-electric cars due to the energy required to manufacture hybrid batteries.)

Analysts have since repeatedly proved the case against CFLs wrong using life cycle analysis, a technique that compares the environmental effect of products from production through disposal. The manufacturing of any light bulb represents a tiny fraction of the energy itconsumes over its lifetime — which is around 2 to 5 percent, depending on the model — so differences between bulbs are insignificant compared with the energy used during operation. Moreover, a CFL bulb lasts about 10 times as long as an incandescent bulb, so the effects of manufacturing are spread over a longer lifetime. In the end, most analysts find that CFLs use approximately one-fourth as much energy as an incandescent bulb overall.

For savvy bulb buyers, CFLs are already old news. The LED is catching consumers’ eyes these days. Unlike CFLs, which are filled with gas, LED bulbs emit light by passing electricity through a solid semiconductor material. It’s the same technology used in cellphones and some high-definition televisions. Unsurprisingly, the same critique that was used against CFLs — that manufacturing is so energy-intensive that it outweighs the energy savings during the bulb’s lifetime — is now being leveled at LEDs. Once again, that argument turns out to be wrong.

And what about mercury?

In February, the Department of Energy released a life cycle analysis comparing LEDs to CFLs and incandescent bulbs. CFLs and LEDs finished in a statistical dead heat. (As expected, incandescent bulbs finished a very distant third.)

LEDs use less energy than CFLs in your home, but their manufacturing and packaging is slightly more energy-intensive. Most analysts, however, expect LEDs to eventually surpass CFLs in lifetime efficiency. As with most new products, there’s plenty of room to improve the manufacturing efficiency of the LED.

Also, while CFLs have basically reached their peak energy efficiency after decades of tinkering, we are likely to see increasingly efficient LED bulbs entering the market in the next five years. (To make an analogy, CFLs are likely to become the cassette tapes of lighting. They may have vanquished the original technology, but their run at the top will be short-lived.)

While energy use is the primary issue in most environmental analyses, one additional factor must be addressed when discussing light bulbs: mercury.

Critics of CFL bulbs have argued that the small amount of mercury in the bulbs presents a significant environmental hazard at the end of the bulb’s life. But if you get much of your electricity from coal — and many people in the Washington region do — producing the electricity that powers the bulb releases far more mercury than the bulb contains.

In addition, big-box stores all over the country accept CFLs for recycling of their component parts, so there’s no reason for most such bulbs to release their mercury into the environment.

In any event, don’t let a fear of mercury in CFLs drive you back to incandescent bulbs: There’s no mercury in an LED.

The LED bulbs might cause a bit of sticker shock, with some selling for $20 to $45, much more than CFLs. But given that the best LEDs now last for approximately 20 years, they should pay off in the long run. And think how much gas you’ll save by not driving to the store for more bulbs.