Explanation/Reference:
The focus of utility computing is the business model on which providing the computing services are based.
The main benefit of utility computing is better economics. Corporate data centers are typically underutilized. Utility computing allows companies to only pay for the computing resources they need, when they need them. Utility computing is very similar to public cloud computing, except perhaps it doesn't necessarily imply self-service, elastic capacity, or multi-tenancy. It does imply pay-per-use.
Note: Utility computing is an on-demand approach that combines outsourced computing resources and infrastructure management with a usage-based payment structure. It covers the packaging of computing resources, such as computation and storage, as a metered service similar to a physical public utility. Utility computing has the advantage of a low or no initial cost to acquire hardware as computational resources are essentially rented.
Reference: Oracle Reference Architecture, Application Infrastructure Foundation, Release 3.0