Clean Water Affordability Act of 2014 - Amends the Federal Water Pollution Control Act (commonly known as the Clean Water Act) to revise and reauthorize through FY2019 a grant program to intercept, transport, control, or treat combined sewer overflows (CSOs) and sanitary sewer overflows.

Requires the Environmental Protection Agency (EPA) to establish a comprehensive and integrated planning approach to the obligations under the National Pollutant Discharge Elimination System (NPDES) of a publicly owned treatment work (POTW) or a publicly owned municipal separate storm sewer system (MS4). Allows approval of a NPDES permit under a state-administered program with a term of between 5 and 25 years if a POTW or MS4 has an integrated plan approved under this Act.

Requires the EPA to: (1) amend the CSO control policy to allow a POTW with an approved long-term control plan to modify the plan to incorporate green infrastructure and energy-efficient technologies if they are cost-effective, and (2) allow a POTW 30 years to meet compliance obligations under a modified plan.

Requires the EPA to: (1) promote the use of green infrastructure in permitting programs, planning efforts, research, technical assistance, and funding guidance; and (2) establish a voluntary green infrastructure portfolio standard to increase the percentage of annual water managed by eligible entities that use green infrastructure.

Requires the EPA to update the guidance entitled "Combined Sewer Overflows - Guidance for Financial Capability Assessment and Schedule Development" to ensure that the evaluations of financial capability assessment and schedule development meet specified criteria.