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Planet Money: AC Power Versus DC Power Grid


We don't think very much about what happens behind our electrical outlets, how the power gets into our homes. But Audrey Quinn of our Planet Money team reports that a lot of people are starting to wonder if the way we deliver electricity is wrong for the modern age.

AUDREY QUINN, BYLINE: Fraida Fund lives in Brooklyn. And her home probably looks a lot like yours. She's got a bunch of electronics. And in order to plug those into the wall, she has those black cords with the boxes on them.

FRAIDA FUND: This right here looks like the charger for the cordless phone. This looks like the laptop charger. I believe this one over here goes to our printer. This one is a cell phone charger.

QUINN: Fund happens to be an electrical engineer. So she knows that power comes into these little boxes from the outlet on the wall in the form of AC power, alternating current. Fund explained to me that in alternating current electricity, the electrons are pulsing back and forth.

FUND: An AC power signal would sound like a siren.

QUINN: So AC would be like (imitating siren).

FUND: Sure. You're very good at that.

QUINN: These black boxes convert the AC power from the outlet into DC power, direct current.

FUND: (Laughter) And DC power would sound more like a steady tone.

QUINN: (Imitating steady tone).

FUND: Exactly.

QUINN: The reason we have this system goes back to the late 1800s. Back then there were two competing power grids, one for AC and one for DC. Thomas Edison was the guy for DC power. And Nikola Tesla was all over AC. Tesla's AC power was way better at traveling long distances. It won out and became the only grid we have, which brings us to a problem today. If you wired AC power to, say, your laptop...

FUND: You'd probably see a puff of blue smoke, and you'd never be able to use it again.

QUINN: Your electronics want DC power. The converter boxes are a fine solution except for this one thing, and you've probably noticed this. They get hot.

FUND: So that's actually loss that you're feeling, when it gets warm.

QUINN: Energy that's lost to heat. In all this AC-to-DC converting in the little black boxes, it ends up wasting about a fifth of the electricity your house takes in. So a bunch of companies are saying, let's get people DC power so they can plug their electronics direct to DC, no conversion needed. And just like there's a standard AC power plug, they're trying to figure out a standard way to make machines plug into DC. Cisco, GE, Philips, a bunch of big universities, they're all on board.

PAUL SAVAGE: In our lifetimes, the way we use electricity has gone from 80 percent AC, 20 percent DC to completely flipped around.

QUINN: Paul Savage helps put in DC power systems in commercial buildings in Detroit. His company's called Nextek Power Systems. He thinks these kinds of DC systems will be in houses soon too. It's not like all our power lines or even all our wall sockets would switch to DC. Instead, you'd have this one super-efficient DC converter box in each room that you'd plug your electronics into. Of course, getting homeowners on board for something like that will take a little while. We'll need new or at least modified devices with DC plugs on their cords. But Savage says in the long run, it'll be worth it. Our homes will be way more efficient and safer. Touch an AC wire, and you'll go...

SAVAGE: I would say it would be, ow.

QUINN: And then what about when you get shocked by DC?

SAVAGE: The DC sound is, hmm.

QUINN: At low voltages, like the kind of power in a house, DC is much safer than AC. Audrey Quinn, NPR News, New York. Transcript provided by NPR, Copyright NPR.

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