State seal of Maine

Maine’s Renewable Portfolio Standard (RPS) is intended to increase use of renewable resources in the state by establishing the minimum amount of renewable energy that the state's electricity providers must sell in a given year. This legally-established renewable energy procurement goal gradually increases over time to meet the overall target of 40% renewable power by 2017.

The state profile below explores the design of this policy, highlighting the factors that influence the success of Maine’s RPS goals and the tradeoffs inherent to it. Once you’re comfortable with the information on this page, you can evaluate the policy’s expected viability with the RPS Feasibility Calculator. You can also use the calculator to change the policy requirements, trajectory, cost cap, and more, to see how altering Maine’s policy design affects its success.

RPS Snapshot


  • 40% of the state's retail electric sales from must be from renewable sources by 2017, subject to the cost cap
  • Carve-out for new renewable generation
  • Implicit ‘cost cap’ defined by compliance payments


Carve-outs can create economic opportunities in the state by introducing new or promising technologies into the market. However, these standards limit the utilities’ ability to substitute between renewable energy sources, potentially increasing the cost of the policy.

Maine’s RPS requires that 1% of the state’s retail electric sales in 2007 come from ‘new’ renewable resources, or resources that came online after September 1, 2005, increasing by 1 percentage point per year to a 2017 goal of 10% of retail sales. In the statute, these resources are termed ‘Class I’. ‘Class II’ resources are old or existing renewable or ‘efficient’ forms of generation. Class II resources comprise a steady 30 percentage points of Maine’s annual renewable obligation. The state had already exceeded compliance with the RPS’s Class II goal when the rules were passed in 1999.

RPS Progress

Compare the goal established in the RPS to what is being achieved.

Energy Details

Grid Mix

The following chart compares the variety of sources currently used to generate Maine’s electricity. The color of each bar is indicative of the carbon intensity of each source.

Cost Cap Details

Maine does not have an explicit cost cap. However, by allowing alternative compliance payments (ACPs), Maine sets an effective cap on the premium a utility will be willing to pay for renewable energy. The RPS allows the Maine Public Utilities Commission (MPUC) to set this cap. In 2011, this rate was $62.13. If the renewable energy premium exceeds this cap, the utility would prefer to meet the standard by making the lower cost alternative compliance payments. The MPUC can suspend the percentage increase in the Class I carve-out for one year if ACPs account for more than half of the state’s renewable obligation in three consecutive years. Revenue from ACPs is paid into the Renewable Resource Fund, administered by the Efficiency Maine Trust. Using the RPS Feasibility Calculator you can make adjustments to cost of alternative compliance, determining how this impacts the provision of renewable power and the overall viability of the RPS.

Historic retail prices (¢ / kWh)

The above chart presents historical data from the Energy Information Administration (EIA) on the price at which residential customers can purchase electricity. Typically, states set explicit cost caps relative to the retail price (as opposed to the lower wholesale price).



Maine’s RPS was enacted in 1999 and required 30% of each electricity provider’s supply to come from renewable energy. Updates since 1999 have amended the original RPS mandate. At the time of the 1999 mandate, renewable capacity exceeded the 30% requirement. The purpose of the later revisions to the requirement have been to develop electricity procurement plans for renewable power beyond the existing capacity. The current legislation more specifically: an additional 10% of capacity to total 40% of renewable power annually by 2017. Renewable energy may be bundled with GIS certificates, which are similar to RECs, to meet Class I requirements, but not Class II requirements.

RPS Technical Details

Eligible Technologies Solar Thermal Electric, Photovoltaics, Landfill Gas, Wind, Biomass, Hydroelectric, Geothermal Electric, Fuel Cells, Municipal Solid Waste, CHP/Cogeneration, Tidal Energy, Fuel Cells using Renewable Fuels, Other Distributed Generation Technologies
Geographic Eligibility RECs (GIS certificates) produced in NEPOOL are acceptable to meet Maine’s renewable obligation. Credit multipliers aim to incentivize ‘community-based renewable energy production’.
Percent of Total Load 98.3%
Technology Requirements Class I or ‘new’ sources account for 10 percentage points of the 2017 RPS obligation
Sectors Investor-Owned Utility, Retail Supplier
Penalty Alternative compliance payments (ACPs) for the renewable portion of the legislation were originally set to $57.12/MWh in 2007, and is adjusted annually for inflation. The ACP for 2013 is set at $65.28/MWh.


Tools and other links