No, absolutely not. You can have one IP address for as many customers as you need(1). For redundancy purposes, however, we recommend that you purchase the Dual-IP service so that you have both a Primary and Secondary IP address to configure on your panels that support it. Additionally, for maximum flexibility, you may want (and technically need) to get a different IP for each of your central station providers if you have more than one.
(1) Although the KeepYourIP™ system can handle large amounts of customers, a practical limitation may be imposed on dealers that show an extremely large amount of internet traffic coming from their underlying customers.