The zone of state toll systems that are part of E-ZPass now stretches far beyond the New York metropolitan area where it began. Now you can use your E-ZPass in toll-zapping booths in 14 states, a vast road-trip zone stretching from Virginia to Illinois to Maine. It’s all a compatible system, but different states set their own fees to issue the transponders and maintain your account.

What not all consumers know is that you don’t have to buy your pass from the state where you live, and you can save money by ordering from across the border. Whether this is a good idea or not depends on where you live, and on where you drive.

Jonathan, a Maryland resident who is the proud new owner of three FastLane devices from Massachusetts, writes:

The opening of a new highway in the Maryland suburbs outside of Washington DC will probably drive many, many citizens in the area to purchase the toll road EZPass. EZPass is the device that is linked to your credit card, and once placed in your windshield, allows you to drive right through a toll booth without stopping. The toll is then automatically applied to your credit card.

The same EZPass device you put in your car can be used on highways in over a dozen states in the northeast. Most people will purchase EZPasses through their home state. But what most people don’t know is that you don’t have to buy the EZPass in the state you live. This is important to know because each state charges a different amount for the exact same device. For example, Maryland charges a non-refundable fee of $21 per transponder, and a $1.50 per month account maintenance fee. At the other end of the spectrum, Massachusetts charges neither of these fees.

I live in Maryland, obtained 3 devices from Massachusetts, and had them in less then a week. No fees, no monthly charges. Sweet.

NOTE: All states require a “pre-paid” amount, usually around $20 to be placed on your credit card. Once the amount in your account dips to something like $10, then the credit card is charged, bringing your account back to the set minimum.

Whether this is a good idea for you depends on where you live, where you drive, and whether your local highway system offers discounts on certain routes to holders of their own tag. Some states charge a monthly fee for the tag, but offer discounted tolls. For example, the tolls from my house to Consumer Reports headquarters run $11.80 if I pay cash, but $11.21 with an E-ZPass. That’s couch-cushion money at first glance, but adds up if you travel toll roads frequently.

Do your research first, and know your own driving habits: even those fees might balance out.

Editor's Note: This article originally appeared on Consumerist.