Verizon today finally followed its wireless rivals in offering clear discounts on service when you pay for your own phone. That extends an offer which previously only applied to customers who were buying the phone on an installment plan from the company. While Verizon has come late to the party, it's certainly now on board and that offers existing and prospective customers a chance to save money. As always, though, there are some confusing details to sort through. To help you determine whether Verizon's latest deal makes sense for you or not, we'll break it down here.

Bring your own phone, get a discount?

T-Mobile upended the industry last year with its "Un-carrier" approach, which included an end to contract plans. But it also put an end to discounted, subsidized phones along with them. At least sort of. By breaking the phone cost out separately and billing you for it over 24 months, the carrier made it clear that you were always paying the full price of your $199 iPhone, even if it didn't seem that way when you plunked down two Benjamins to get it in the first place. The key was that in exchange for explicitly making installment payments on the phone, T-Mobile lowered the price of your monthly bill. And once the phone was paid off, if you chose to keep it, you could enjoy a lower price going forward.

When AT&T and Verizon first attempted to match T-Mobile's offering, they almost comically began offering monthly installment pricing on phones while leaving out the monthly discounts. This made the first response easy to ignore. AT&T fixed its offering in December and yesterday Verizon joined the party as well. (Verizon's new offer begins Thursday and neither company is promising these will last forever, but it's easy to imagine them becoming permanent).

To get the lower monthly bill, you're going to have to either pay the full price for a phone, which can range up to $750 for a 32GB iPhone, or buy it over time. The installment plans are called AT&T Next and Verizon Edge. (Update: With Verizon, you have to buy the phone over time to get the discount. If you pay in full for a phone, the company isn't doing anything for you, even though they ought to.) Typically, they allow you to spread that big expense over 2 years without adding any interest cost. That $750 iPhone, for example will run you $31.24 a month on Verizon, for $749 and change -- almost exactly the same amount as buying it outright. There's almost no downside to taking Verizon's low-cost financing. In fact, if you want to upgrade early, once you've paid off half the phone you can trade it in and start the process over again with a brand new model. The only way to do that on contract is to sell your phone independently and buy a replacement at full price; that's much less convenient even when the net cost is comparable.

What do the savings look like?

The question then, is what do you get in return for taking one of these plans? The answer will depend on how much data you purchase every month. Both AT&T and Verizon reserve the best discounts for customers with 10GB or more of monthly data, which costs $100 from each carrier. On top of that, you'll pay an "access fee" for each smartphone that shares the data. Normally, that's $40 a month per phone. So a typical family of four with a plan like this will pay $260 a month plus taxes. (Note that most families of four don't actually use that much data and could get by with a smaller plan.)

But if you don't take $199 iPhones, or the shiny new Galaxy S5 from Samsung, and instead bring your own phone from another carrier -- assuming it's compatible, which either carrier can help you determine -- or buy it with Verizon Edge, the company will knock off $25 from that $40 fee, bringing it down to $15. AT&T will do the same. So now, if all four of you are doing that, the $260 can be brought down to $160. This is pricing in the ballpark of what the next tier of carriers offers, although T-Mobile has recently done things like bringing back unlimited data of sort, which can make their pricing more attractive still. Now, of course, if everyone is paying $31 and change for an iPhone or Galaxy, the monthly bill will not be $160 but rather $285. But consider that instead of shelling out $800 initially on phones as well as $260 per month, you now start out paying nothing and only increase monthly payments by $25.

The customer wins, at last?

This deal starts to look pretty good, but there are caveats. First, if you are buying less than 10GB per month, the per-line discount is only $10, not $25. Our sample family would see its monthly bill