Google Project Fi will no longer charge you for more than 6GB of data

To date, Google Project Fi has adopted a $10-per-1GB rate for data. You basically tell Google how much data you think you’ll use each month, and then either get reimbursed for data you didn’t use, or you pay a little extra if you go over that amount. Bill Protection changes that a little — you’ll still pay $10 per 1GB, but if you go over 6GB of data, your bill will be capped at $60. Combined with the $20-per-month base fee for Project Fi, that means you won’t ever pay more than $80 in one month unless you choose to.

Google also notes that those who use more than 15GB of data may see a decrease in their speed. Less than 1 percent of Project Fi users currently use more than 15GB of data, though that could very easily change with cheaper access to that much data. You can also opt out of the slow data speeds by simply continuing to pay $10 per 1GB — though obviously that will get a lot more expensive.

Bill Protection also applies to group plans, though when it kicks in depends on how large your group is. Google has launched a calculator for that here, showing that it will kick in at 10GB for two people, 12GB for three, and so on.

The plan is different than other unlimited data plans, and in a way that could make it a lot cheaper. Why? Because on months where you don’t need as much data, you won’t have to pay for it. If you use 1GB in a month on T-Mobile‘s unlimited data plan, you still have to pay $70 for your plan. If you use 1GB on Project Fi, you’ll only pay $30 ($10 for the data, $20 for the base fee).

Bill Protection is rolling out today, and if you’re a Project Fi subscriber, you’ll see it show up in your next billing cycle. New subscribers may want to think about joining — Google is offering up to $120 off some of the phones that work on Project Fi for a limited time.

Update: Added Google pricing calculator for group plans.