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In 2007, Congress passed the Energy Independence and Security Act, which mandated higher energy efficiency standards in the US. The law included new standards for light bulbs that were written to spur the lighting industry out of the incandescent age and towards new technologies like LEDs that use significantly less energy.

It worked. As manufacturers adapted to the incoming standards, hardware store lighting aisles began to fill with new LED options, and consumers started buying them in order to reap the energy savings. The national energy use attributable to lighting plummeted -- in 2018, both the residential and commercial sectors used less than half as much energy to power their lights as they did in 2001.

But last month, the Department of Energy under President Donald Trump reined those standards in by limiting the types of light bulbs to which they can apply. Those revised exemptions, which kick in Oct. 7, will protect the sale of certain kinds of incandescent light bulbs that might otherwise have come off the market in the coming months due to poor energy efficiency.

"This action will ensure that the choice of how to light homes and businesses is left to the American people, not the federal government," said a DOE spokesperson in a statement. The move would eliminate a "cost burden on American consumers and businesses."

That's set off a battle with efficiency advocates, who say the White House is trying to undermine bipartisan legislation that was working as intended to combat climate change and increase America's energy independence. Sure, it's a wonky fight, but an important one that affects all of us. Here's everything you should know.

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How did we get here?

First, some quick background on how the law has evolved. Let's start almost 45 years ago, when Congress passed the Energy Policy and Conservation Act of 1975, which was signed into law by President Gerald Ford. The US had just been through a severe oil shortage in 1973, so the law sought to create a comprehensive federal energy policy to help prevent or mitigate future energy crises. This is really when the modern concept of "energy independence" first found its legs.

Along with establishing the strategic petroleum reserve, it established the Energy Conservation Program for Consumer Products, which gives the DOE the authority to develop, revise and implement minimum efficiency standards for consumer appliances -- including light bulbs.

Fast forward a few decades to 2007 when Congress passes the Energy Independence and Security Act, and President George W. Bush signs it into law. Among other stated purposes, like increasing the production of clean, renewable energy, the bill aimed to increase efficiency standards for public buildings and consumer appliances. In the case of light bulbs, the law required an efficiency bump of roughly 25%, which was phased in from 2012 to 2014. The law calls for even higher efficiency standards to take effect next year.

How much higher?

The 2007 law mandates energy savings at least as good as what we'd get with a minimum efficiency standard of 45 lumens per watt for the most common types of light bulbs.

For reference, a typical, 60-watt incandescent light bulb puts out about 15 lumens per watt, if not less. A halogen incandescent version of the same bulb will do slightly better, but still isn't likely to go much higher than 20 lumens per watt.

Meanwhile, spiral fluorescent bulbs (CFLs) fit the bill at about 65 lumens per watt -- but best of all are bulbs that use light-emitting diodes, or LEDs. They can put out 80 or even 100 lumens per watt, so they only need to use a fraction of the energy that incandescents use.

The DOE can set whatever standards it deems appropriate within the law's framework to get us to that 45 lumen-per-watt standard, but if it drags its feet or if it doesn't hit that goal, then a backstop provision is supposed to kick in. That backstop simply says that the Secretary must prohibit the sale of bulbs that put out less than 45 lumens per watt, effective Jan. 1, 2020.

So, in a sense, the Energy Independence and Security Act gave the DOE 13 years to get us to an efficiency standard of 45 lumens per watt, or better. That deadline is three months from now.

Enlarge Image US Energy Information Administration

Was the law working?

Yes. Manufacturers pumped resources into improving LED technology, and innovations from new competitors helped bring costs down. As more people started buying in, the amount of energy used to light our homes and businesses dropped sharply, particularly between 2015 and 2018.

"The 2020 lighting standards are the main reason we have so many LED choices to pick from today," says Noah Horowitz, a director at the Natural Resources Defense Council, an environmental advocacy group.

One good example is the North Carolina-based lighting manufacturer Cree Lighting. When it began making and selling residential LED light bulbs in 2013, they were $10 apiece. But today its newest bulbs cost a little under $4 each, and others like them are available for even less.

"Back in 2013, $10 was a steal for an LED light bulb," says Phil Primato, Cree Lighting's director of consumer retail. Primato adds that Home Depot's Ecosmart house brand now sells LED bulbs for as little as $1, matching the traditional price of incandescent bulbs. "There are LED options that are around that price point today if your sole desire is to shop on price."

But there's more to consider than just the upfront cost of LED bulbs. You should factor the energy savings in, too.

Chris Monroe/CNET

For instance, a 60-watt-replacement LED will typically consume around 10 watts or less and add about $1 to the average yearly energy bill. That bulb will last you a decade or longer. A 60-watt incandescent bulb that's just as bright will add about $7 to your yearly bill, and you'll need to replace it much sooner. Even if the incandescent is free, it still costs you more than a full-price LED after just six months of use.

Math like that coupled with reasonable upfront costs is a win for consumers and the environment alike, and the 2007 law is what spurred the market into getting us there. But experts say there's still room for progress.

"While LED prices have come way down, inefficient incandescent and halogen bulbs still represent a third or more of new light bulb sales," Horowitz says. "The standards are needed to ensure that an energy saving bulb goes into each of the more than 1 billion sockets that still contain an inefficient bulb."

Now playing: Watch this: How to buy bright LED light bulbs that don't suck

Jane Harman, a former Democratic representative for California who co-authored the 2007 light bulb standards with Michigan Republican Fred Upton, suggests the benefits of LED lighting go beyond saving consumers money.

"The electricity saved by efficient bulbs protects the climate and also has immense national security benefits," Harman wrote earlier this year in an op-ed for The Hill. "The less energy a light bulb uses, the less energy a household demands, and the less energy the US uses overall.

"National security is relevant in that the less energy the United States demands, the less it needs to rely on oil, gas and coal imports," Harman added. "As indicated by its name, the Energy Independence and Security Act was intended to address such issues and, along with the economic benefits, the focus on national security is what created the space for bipartisan consensus."

So what's changing?

Technically, no standards are changing -- at least not yet. Instead, what the DOE is proposing is to narrow the number of bulbs to which those rising standards will actually apply.

Chris Monroe/CNET

When the Energy Independence and Security Act was first signed into law, it applied the rising standards to "general service lights," a broad industry term that refers to commonly used household light bulbs. That category includes compact fluorescent bulbs, LED bulbs and traditional incandescent bulbs. But exempted from the new standards were certain specialized incandescent bulbs, including three-way bulbs, shatter-resistant bulbs, and differently shaped bulbs such as floodlights, candelabra lights and bathroom vanity globes.

The Energy Independence and Security Act instructed the DOE to reconsider those exemptions twice before 2020 to determine if they were still necessary. Towards the end of the Obama administration, that's what the DOE did. Ultimately, it decided that many of those exemptions could reasonably be lifted without creating an undue burden on the industry. Thus, the rising standards would apply to them as well, effective Jan. 1, 2020.

Now, under President Trump, the DOE is using the mandate for a second checkup on those exemptions to basically click undo on that Obama-era decision.

What's the impact of that?

First off, you won't notice any changes in energy rates or the price of light bulbs. Demand for LEDs continues to grow, and the industry will continue to move in their direction.

Still, reinstating those exemptions and taking those bulbs back out of the equation is a significant reversal. According to a 2017 report from Lawrence Berkeley National Laboratory, exempted bulbs like those have a nationwide installed stock about 80% as large as the regular, nonexempted bulbs.

"They offer a disproportionately large potential for energy savings since the vast majority are currently traditional or halogen incandescent lamps," the report's authors add. Holding bulbs like those to the backstop standards of the Energy Independence and Security Act would yield an estimated carbon dioxide emissions reduction of 540 million metric tons by 2030, as well as energy savings that are 35% greater than the total energy consumption of the entire US residential sector in 2016.

Exempting those bulbs could impact progress in other, nonexempted categories, too. Efficiency proponents point out that some manufacturers have used the exemptions for industrial rough service and shatter-proof bulbs to make and market incandescent "loophole lamps." Lights like those are typically just regular, inefficient incandescent bulbs with a special coating on the glass that makes them more durable -- and, thanks to the exemption, it helps them dodge that backstop, too.

"These loophole lamps are especially bad deals for consumers," those critics say, pointing out that a 75-watt replacement rough service bulb "would increase a consumer's energy costs by more than 250% compared to a standards-compliant halogen bulb." Make that more than 600% compared to an LED.

Still, light-bulb buying habits are often based on familiarity. As normal incandescent bulbs started to disappear from store shelves, sales for those lookalike loophole lamps surged, growing from 914,000 in 2011 to more than 7 million in 2015. Under the backstop provision, which efficiency proponents argue has already been triggered, the DOE would have been required to prohibit the sale of bulbs like those starting in January. Now, the DOE wants to re-exempt them from the rising standards -- and it also argues the backstop hasn't been triggered at all.

Enlarge Image Cornell Law

Is the backstop triggered or not?

Think of the backstop provision in the Energy Independence and Security Act like an efficiency safety net. It's a protective layer of law to keep the DOE from backsliding to standards less efficient than what Congress agreed upon in 2007. The question of whether or not that backstop has already been triggered is a contentious one.

There are a few specific things that can trigger it. First, the law established a 2014 deadline to evaluate whether standards could be raised and exemptions lifted. Missing that deadline triggers the backstop. Same goes if the DOE were to change the standards for incandescent lights without issuing a final rule by 2017.

And, as said earlier, the DOE's efforts have to amount to energy savings greater than or equal to what the backstop would produce -- otherwise, it kicks in like a failsafe to get us to a guaranteed 45 lumens per watt on Jan. 1, 2020.

Critics of the DOE argued it had failed to meet both the 2014 and the 2017 deadlines, and thus triggered the backstop. The DOE rebuffed the argument for the latter, pointing out that it had never determined whether or not to change the standards for incandescent bulbs, and therefore wasn't under any obligation to issue a ruling on the matter at all.

As for the 2014 deadline to evaluate overall standards and re-examine the exemptions, the DOE says that it didn't issue its determination on the matter until 2017 because of a 2014 appropriations bill that blocked it from implementing or enforcing any standards for incandescent bulbs, but that the process had already begun.

"DOE initiated the first General Service Lighting standards rule-making process by publishing a notice of availability of a framework document in December 2013," the DOE wrote this past February. That, the DOE argues, satisfies the 2007 law's requirement that "not later than Jan. 1, 2014, the Secretary shall initiate a rulemaking procedure" that re-evaluates light bulb standards and exemptions.

So, if not the backstop standard, then what? The DOE hasn't offered up any alternatives yet, but its most recent filing says that it has no plans to change the specific standards for incandescent bulbs, and that it plans to make a separate determination about what to do with the overall standards for household bulbs.

"The legal issues tied to the light bulb standards are rather complex," admits Horowitz. "It's also quite the head-scratcher that we are just a few months from Jan. 1, 2020 and DOE still hasn't completed it's work."

How does the lighting industry feel about this?

"It is important to note that this was not a 'rollback,'" says Tracy Cullen, a spokesperson for the National Electrical Manufacturers Association. With a board of governors that includes executives from lighting aisle mainstays like Lutron, Leviton and Philips Lighting parent company Signify, the trade organization voiced support for the DOE's move to limit the scope of the rising standards, and maintains that no specific standards have actually changed.

GE Lighting

"The significance of those facts is that it belies DOE is rolling back standards or backsliding in some way because there are no standards to roll back from," Cullen told CNET.

Many in the lighting industry -- particularly manufacturers like Signify, Ledvance and GE Lighting that continue to make and sell incandescent bulbs -- seem to be circling the wagons around that position.

"Signify supports the transition towards energy-efficient LED and connected LED lighting, and in fact, we are driving this transition with our innovations," a Signify spokesperson says. "We support DOE rules that allow for an orderly phase out of older technologies, where necessary and applicable (meaning that the measure will lead to the desired result)."

"The US Department of Energy's announcements align with Congress's intent in 2007 when it enacted the Energy Independence and Security Act," says Jennifer R. Dolin, head of government affairs and sustainability at Ledvance, which makes Osram and Sylvania-branded bulbs. "The future of lighting is LED technology, evidenced by the declining sales of halogen and CFL light bulbs, and additional standards aren't needed to catch up with a transformation that's already taking place."

GE Lighting declined to comment for this story.

One exception to the wagon-circling is Cree Lighting, which only makes LEDs and doesn't dabble in incandescents at all.

"The rest of the industry, for the most part, is conflicted," says Primato. "They still make and sell a lot of the previous-generation types of products.

"I don't really see our behavior or retailer behavior or consumer behavior changing dramatically, regardless of the legislation, or regardless of anything that the administration continues to say about incandescent light bulbs," Primato says, nodding to recent remarks from President Trump blaming energy-efficient light bulbs for his skin tone.

"I'm not sure that any light source is necessarily responsible for the President's hue," Primato says.

So what happens next?

Per the DOE, the reinstated exemptions take effect next week, on Oct. 7. After that, the next step is a public meeting on Oct. 15, where the DOE will allow interested parties to share their views on issues that might affect its determinations.

Meanwhile, efficiency advocates tell CNET they plan to continue fighting to maintain the standards of the Energy Independence and Security Act.

"DOE has misread the law," says NRDC's Noah Horowitz. "NRDC will continue to oppose the Department's unlawful rollbacks at every opportunity, including possible litigation."