I’m standing in the penthouse suite of the Hard Rock Hotel and Casino in Las Vegas, looking at what seems to be a large subwoofer on a shelf. A TV remote sits on an ottoman about eight feet from the shelf, with no buttons illuminated. Energous CTO Michael Leabman taps his iPad, triggering the black speaker-like device, and after a quiet second the remote’s lights flicker on. In another demonstration, the remote is brought within 2 feet of an object that looks like a soundbar, and again comes to life.

Voilà, wireless power.

Quartz/ Dave Gershgorn Energous’ power from a distance.

In another demo room, tucked behind the construction of the CES show floor before the convention starts, Ossia CEO Hatem Zeine shows me a simple, battery operated clock. An engineer clicks a button on his computer, and the clock stops, its source of power interrupted. Again, voilà.

These aren’t the only tests I was shown by each company, but the most demonstrative. Each company jumped through hoops to show their technology wasn’t a sham, that they really could achieve Nikola Tesla’s dream of power over the air.

Conducting or transmitting electricity through their air has vexed physicists for years. Sending power over a distance has even eluded much of science fiction. (Even Star Wars’ lightsabers need to be recharged, per a deleted Episode 1 scene.) In recent years, the internet has given rise to charlatans claiming to have the easy solution for wireless power. uBeam, a company backed by venture capital that seemed to have an early lead in the space, has been the source of controversy after a former VP of engineering accused the company of being fake. The demos I viewed could have been an elaborate show of smoke and mirrors, but from what I could see, they worked.

These two companies, Energous and Ossia, don’t agree on much—they’re locked in battles for many of the same licensing agreements with major tech companies—but they do both say that the only thing holding back their technology from the market is the Federal Communications Commission, the government agency that must approve any devices that transmit wirelessly. They expect the FCC to begin approving devices in the first half of 2017. Another source in the wireless power industry agreed with the two companies on the FCC timeline. The FCC did not immediately respond to a request for comment.

Quartz/ Dave Gershgorn Ossia demonstrates its power at a distance with a energy-detecting spoon.

Energous, which touts it will have the technology to charge devices from 2-3 feet in the market by the end of 2017, wants to send enough power to charge a cell phone (5 watts) within 5 feet. They’ve tested the technology at Underwriters Laboratories, confirming the assessment and also delivering 1 watt of power at 10-15 feet. However, the technology only works when there’s a clear line of sight between the transmitter and the device.

Ossia says that any competitors who claim to send this much power put people at risk. Instead, it sends lower wattage on well-established frequencies. Ossia has passed FCC safety tests used to regulate wi-fi and bluetooth and published patents. For its part, Energous points to its partnerships as proof of safety, saying it has begun selling FCC-approved devices based on the same technology that transmit power within millimeters, rather than feet.

In short, Energous offers more power to stationary objects directly in front of the transmitter, while Ossia provides less power, but for moving objects and those not in line of sight, and over an established frequency band.

This battle is reminiscent of Thomas Edison and Nikola Tesla’s War of the Currents, where Edison’s direct current (DC) was pitted against Tesla’s alternating current (AC). Attempting to win lucrative contracts, Edison famously used elaborate plots to convince investors and the public that AC was too dangerous for the home, like getting New York state to begin using AC power for execution by electric chair.

Even so, we plug into AC outlets today, of course, and wireless power at a distance is similarly shaping up to be a zero-sum game—the technology is only convenient if it’s everywhere. For instance, you might not be able to charge a Samsung phone with an iPhone Lightning cable, but you plug them both into a standard AC outlet. These companies are competing to be the outlet.

Energous is alleged to have a contract to provide Apple’s wireless charging, something the company’s CEO hinted at during our interview, although that contract would preclude it from developing the technology for another phone or similar device until that company has shipped a product. Ossia doesn’t have a major partnership announced yet, but focuses on the fact that its technology is safe, above all.

Quartz/ Dave Gershgorn Energous’ long-range power transmission.

“Delivering power to multiple devices, out of line of sight, safely. We’ve done it, and I can tell you there is nobody that is even close it,” Ossia’s Zeine told Quartz.

There’s also the matter of how the technology will fit into everyday life. In both demonstrations the transmitters were prohibitively large for home use. Ossia’s new Cota tile is recessed into the ceiling, or transmitted from a large device that looks like an air purifier. Energous’ short-range transmitter was housed in a repurposed sound bar, about 2 1/2 feet long and 4 inches tall. Their long-range transmitter was the size of an 8″ subwoofer.

For those reasons and more, the charging industry of today says power at a distance is going to be an auxiliary charging method, while inductive charging (when the phone is placed on a power-conducting matt, like Qi) will be the preferred method. This is mainly due to the transmitter and current limitations on power at a distance. Both companies say their technologies support sub-5 watt devices. (Qi quick-charging is 15 watts.) However, hundreds of types of devices from smoke detectors to lights to IoT devices don’t need more than 5 watts of power.

“If you’re going to have a wireless charger that’s going to take four hours to charge, then what’s the point if you can just plug it in,” says Edo Campos, head of PR for battery and accessory company Anker.

Chris Burket, senior marketing engineer for TDK’s wireless power division, agrees, maintaining that Qi technology is still way ahead of anything wireless charging can do.

“How do you fast charge if you only get 1 watt?” he says, “It’s impossible.”

But Zeine says it’s still early days.

“When wi-fi came out nobody was saying, ‘Why is the limit 1 megabit per second, and not 100 megabits,” Zeine said.