Traditionally One-time, Recurring, and Usage are the three types of billing models. With the advent of service-based industries, usage-based billing model is quite popular because customers wish to pay only for what they consume.

For example, a high-tech company may offer a monthly cloud-based data storage product.

If a product has the Price Type set to Usage, it is a usage-based product and hence qualifies for the Usage-based billing. When an order containing a usage-based product is activated, a Usage Schedule in addition to the Billing Schedule is generated. You can input the usage volume/quantity through Usage Inputs and derive the usage amount for that input. The net amount due at the time you generate an invoice then depends on the quantity of the units consumed and the per unit price of the product or service. 

You must provide a Usage Input to record the usage quantity consumed within a specific duration. For more details on usage inputs and usage-based billing, refer to Conga Billing Documentation.

Revenue is recognized for a usage-based product once the billing schedules are invoiced and the order reaches Revenue Recognition date.