In cost accounting, overhead costs include all business expenses that are not directly traceable to a specific cost object (like a product or service) but are necessary for general operations. Utilities such as electricity and water for a factory or office fall into this category. While their consumption might fluctuate, they cannot be efficiently allocated to a single unit of production. Therefore, they are considered indirect costs and are grouped under manufacturing overhead (for a factory) or administrative overhead (for an office).

A: Labor costs represent compensation paid to employees for their work, not expenses for utilities.

B: Variable costs are costs that change in direct proportion to production volume (e.g., raw materials). Utilities are not classified this way.

D: Indirect materials are tangible items used in the production process but not incorporated into the final product (e.g., machine lubricants).

1. Horngren, C. T., Datar, S. M., & Rajan, M. V. (2015). Cost Accounting: A Managerial Emphasis (15th ed.). Pearson. Chapter 2, "An Introduction to Cost Terms and Purposes," defines manufacturing overhead as all manufacturing costs other than direct materials and direct labor, citing examples like electricity, water, and rent.

2. MIT Sloan School of Management. (n.d.). 15.515 Financial Accounting, Session 10: Cost Behavior and Cost Estimation. MIT OpenCourseWare. Course materials distinguish between direct costs and indirect (overhead) costs, placing factory utilities in the overhead category.