Tim Cook, chief executive officer of Apple Inc., speaks about the new iPhone during an event at the Steve Jobs Theater in Cupertino, California, U.S., on Tuesday, Sept. 10, 2019.

Apple's annual fall event Tuesday announced the launch of a seventh-generation iPad, the Apple Watch Series 5 and a new gaming subscription service. Apple CEO Tim Cook also disclosed Apple TV+, a video service, will cost $4.99 per month for a family subscription, starting Nov. 1. But the real star of the show each year is always the iPhone, and Apple unveiled three new models: The iPhone 11, the iPhone 11 Pro and the iPhone 11 Pro Max. The new 11 base model features a longer battery life than past models and a 6.1-inch liquid retina display, but the biggest difference is the camera: The 11 comes equipped with a dual-camera system that can take wide-angle photos and videos. It comes in six new colors: purple, green, white, red, black and yellow. The iPhone 11 Pro comes with three cameras, four-times optical zoom and a 5.8-inch "Super Retina XDR" display. It has a matte finish, in one of four colors: space grey, silver, midnight green and gold, and comes in 64 GB, 256 GB and 512 GB. The iPhone 11 Pro Max is the same, but clocks in at 6.5 inches. The iPhone 11 starts at $699, the iPhone 11 Pro starts at $999 and the iPhone 11 Pro Max starts at $1,099. Apple will begin taking preorders on Friday and they will start shipping Sept. 20. If you're looking to upgrade, here's what you need to know to get the best deal.

When to opt into the upgrade program

As mentioned above, the iPhone 11 starts at $699, which is less expensive than last year's iPhone XR, Apple's best-selling model in 2018, which started at $750 (it is now $599) and has a lot in common with the 11. Other high-end iPhone models can cost more than $1,000, making iPhone 11 a pretty good deal, if you need a new phone, considering all of the features and camera quality. There are two main ways to buy a new iPhone: Opt into Apple's yearly upgrade program, or buy a phone outright (you can, of course, buy refurbished phones or wait for a sale on older models, but this is for the new models). If you're an Apple loyalist and want the newest model every year, then the upgrade program makes sense. But if you only get a new phone when you absolutely need one, it might not.

Apple's Kaiann Drance talks about the new iPhone 11. Justin Sullivan | Getty Images News | Getty Images

That's because the upgrade program finances phones over a 24-month period, allowing participants to trade in their phone after half of the phone is paid off, or 12 months. How the math shakes out depends on the phone model, but let's take a look at the iPhone 11 models introduced Tuesday. Here's how much you'd pay for the lowest-capacity version of each new iPhone in the upgrade program (so you may pay more): iPhone 11: $35.33/month for 24 months for the 64 GB phone. That's $423.96 after the mandatory 12 payments.

$35.33/month for 24 months for the 64 GB phone. That's $423.96 after the mandatory 12 payments. iPhone 11 Pro: $49.91/month for 24 months for the 64 GB phone. That's $598.92 after the mandatory 12 payments.

$49.91/month for 24 months for the 64 GB phone. That's $598.92 after the mandatory 12 payments. iPhone 11 Pro Max: $54.08/month for 24 months for the 64 GB phone. That's $648.96 after the mandatory 12 payments. The upgrade includes AppleCare+ for the full 24 months, making it a better deal. But remember, the details of the trade-in program can change at any time. So check Apple's website for terms and conditions before you make any decisions.

When to buy the phone outright

If you don't upgrade every year, then you might want to buy the phone outright, assuming you can afford the $699 starting sticker price. No need to pay more than you have to if you tend to hold on to your phone for at least two years.

Apple's senior vice president of worldwide marketing Phil Schiller talks about the new iPhone 11 Pro. Justin Sullivan | Getty Images News | Getty Images