The ACA covers certain preventive services in full

The Patient Protection and Affordable Care Act (ACA) requires that all insurance policies sold in the Health Insurance Marketplace and in the small group and individual markets cover a set of essential health benefits, including certain preventive screenings without any out-of-pocket costs to the patient. 

Coverage of the screening and preventive services is guided by U.S. Preventive Services Task Force (USPSTF) recommendations. Under the ACA, any preventive service receiving a Grade A or B from the USPSTF is covered at 100% by most health insurers. This level of reimbursement applies to in-network providers only. Preventive care or screenings done by out-of-network providers may result in out-of-pocket costs such as insurance copays or deductibles for the patient.

Essential health benefits are minimum requirements for all ACA Marketplace plans. Specific services covered in each benefit category may vary by state.

Health insurers usually cover medically necessary screening and preventive services not included in the ACA requirements (i.e. mammograms before age 40, colonoscopies before age 45 or breast screening MRIs for high-risk women) but they are not required to cover these services at 100% so patients often have to pay deductibles, coinsurance and copays.