Google's new cellphone service has the best data plan anyone has ever offered

You only pay for the data you use.

How nice does that sound?

Unfortunately, none of the major US wireless carriers offer that. But Google's new wireless service called Project Fi does.

Here's the pricing scheme: You pay $20 per month for unlimited calls, texting, mobile hotspot usage, and international coverage. Then you pay $10 for every gigabyte of data you want to use in a month.

If you don't use all the data you buy, Google refunds you the difference. No other wireless carrier does that.

To use Google's example:

Let's say you go with 3GB for $30 and only use 1.4GB one month. You'll get $16 back, so you only pay for what you use.

Simple.

It's a great deal, and it's something no other carrier offers so far. T-Mobile and AT&T let you roll over unused data to the next month, but you still have to pay the full price for that data whether you end up using it or not. AT&T and Verizon also charge you extra if you go over your data plan. Google is the only company willing to refund you in cash for the data you don't use.

Now for the caveats.

Project Fi is only available in limited areas in the US and it only works on the Nexus 6 phone, which is made by Motorola. There aren't any immediate plans to open Project Fi to other devices like the iPhone quite yet. Google is also using Sprint and T-Mobile's networks to host the data, but Sprint and T-Mobile generally have poorer coverage compared to AT&T and Verizon.

That said, it's a step in the right direction. And if Project Fi or something like it grows big enough, it could entice big carriers like AT&T and Verizon to offer fairer pricing plans too.