This is 99% invisible. I'm Roman Mars.

In the late 1800s, as more and more people began to have electric lights in their homes,

the utility companies began looking for a good way to measure how much electricity each customer

was using.

Actually, way back when Thomas Edison built the first electric power stations, there were no

electric meters in people's homes. So he billed a monthly fee based on how many light bulbs they had.

That's Sam Evans Brown of New Hampshire Public Radio.

That billing per light bulb system wasn't great,

so people came up with a meter that did the job well enough.

It's the same basic meter that most of us in the US

have in our homes today.

And the way it works is when the electricity comes into your house, a little dial turns forward and shows how much you've used.

And even though the original designers never really intended for this to happen,

if you send electricity back into the grid the dial turns backward to show

electricity leaving your house.

Now if you're like me there's no electricity leaving your house it's's only coming in. But if you're like

Sam who has solar panels on his roof, electricity is leaving the house and going

back into the grid. Yeah, that's because my solar panels create more energy than I can use. That excess energy goes back into the grid and out to my neighbors.

And in my state, New Hampshire, I get credited for that extra energy I create.

It's a practice called net metering and for a while it was totally

not controversial, but now it is.

There are huge political battles being fought over this.

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