E15—a fuel blend of up to 15% ethanol and 85% gasoline—generally cannot be sold during the summer driving season (June 1–September 15) because it does not meet gasoline Reid vapor pressure (RVP) requirements, which limit fuel volatility under the Clean Air Act (CAA). The statute allows the U.S. Environmental Protection Agency (EPA) Administrator to issue a temporary fuel waiver of these requirements (42 U.S.C. §7545(c)(4)(C)(ii)) under certain conditions. On March 25, 2026, EPA issued the first nationwide fuel waiver for the 2026 summer driving season. The waiver allows E15 to be sold during the summer driving season, in part, to address extreme and unusual fuel circumstances that EPA states are "the result of ongoing issues in the Middle East, among other events." EPA also states its "intention to issue new waivers effectively extending (renewing) these waivers until such time as the … circumstances described in this action are no longer present."
President Trump's January 20, 2025, Executive Order (E.O.) 14156, "Declaring a National Energy Emergency," included a provision about the year-round sale of E15. The order (Section 2(b)) states,
Consistent with 42 U.S.C. 7545(c)(4)(C)(ii)(III), the Administrator of the Environmental Protection Agency, after consultation with, and concurrence by, the Secretary of Energy, shall consider issuing emergency fuel waivers to allow the year-round sale of E15 gasoline to meet any projected temporary shortfalls in the supply of gasoline across the Nation.
The statutory provision referenced in the E.O. is the third of three factors the EPA Administrator must consider when determining whether to issue a temporary fuel waiver: whether the waiver is "in the public interest." The E.O. directs the EPA Administrator to consider issuing—but does not require the Administrator to issue—temporary fuel waivers that would allow for the year-round sale of E15. In light of the statutory limit that requires waivers to be effective for a period of 20 calendar days or shorter, to achieve the year-round sale of E15, the EPA Administrator would have to issue a series of consecutive waivers as was done for prior summer driving seasons.
Congress has explored legislative options pertaining to the year-round sale of E15. In January 2026, the House passed H.Res. 375, which established an E-15 Rural Domestic Energy Council and directed the council to investigate the sale of E15, to develop legislative solutions, and to submit those solutions to Congress, among other things. Bills in the 119th Congress propose permanent year-round sales of E15 (S. 593 and H.R. 1346). Some Members of Congress request that "[a]ny legislative movement on E15 must be conditioned upon meaningful reforms to the Renewable Fuel Standard (RFS)." E15 legislation was included in a short-term FY2025 spending bill introduced in the House in December 2024 (H.R. 10445, 118th Congress) but was not included in the FY2025 continuing resolution package that became law (P.L. 118-158).
The CAA authorizes the EPA Administrator to regulate fuels and fuel additives. The act regulates (among other pollutants) precursors for ground-level ozone, a primary component of smog, which has been found to negatively impact human health and welfare, among other effects. One of the requirements intended to reduce smog is a limit on gasoline volatility because volatile organic compounds within gasoline evaporate more readily at higher temperatures (e.g., during the summer months) and can contribute to smog formation. RVP is a common metric of volatility—the lower the RVP, the less the substance will evaporate. RVP requirements in Section 211(h) of the CAA—which apply to the 48 contiguous states and the District of Columbia—generally prohibit the sale of gasoline with an RVP greater than 9.0 pounds per square inch (psi) during the high-ozone season (i.e., the summer months). In 2012, the National Renewable Energy Laboratory (NREL; renamed the National Laboratory of the Rockies [NLR] in December 2025) reported that the addition of 10% ethanol to gasoline increases the RVP of the blend by about 1.0 psi.
The CAA provides some exceptions, including a waiver—the "one-pound waiver"—stipulating that ethanol-gasoline fuel blends containing 10% ethanol (E10) are subject to an RVP limit that is 1.0 psi greater than what would otherwise apply given certain conditions (e.g., the 9.0 psi standard for certain areas would subject E10 to a 10.0 psi limit). The waiver does not apply to reformulated gasoline (RFG); there is a 7.4 psi RVP standard for RFG. EPA reports that about 25% of gasoline sold in the United States is RFG. In addition, according to EPA, the waiver "does not apply in areas where EPA has approved a regulation into a state implementation plan (SIP) that limits the applicability of the 1.0 psi allowance." States may petition EPA to remove the 1-psi waiver for gasoline-ethanol blends containing 10% ethanol (E10) (42 U.S.C. §7545(h)(5)). Some states have taken advantage of this option. The regulations for gasoline RVP standards are available at 40 C.F.R. §1090.215.
NREL reported in 2012 that "the RVP impact of 15% ethanol is indistinguishable from that of 10% ethanol in gasoline for all volatility seasons and base hydrocarbon vapor pressures," and "there is no technical reason for treating E10 differently from E15." In general, it appears that greater substitution of E10 with E15 may not lead to material emissions changes; however, there could be other market impacts associated with E15. Thus, the sale of E15 year-round involves other concerns that Congress may consider, including the following: