Renewable Portfolio Standard

Program Renewable Portfolio Standard
Category Regulatory Policy
Implementing sector State
Last Update
State Maine
Technologies Solar Thermal Electric, Solar Photovoltaics

Maine's original Renewable Resource Portfolio Requirement was passed as part of the state's 1997 electric utility restructuring law.  In 1999, Maine's Public Utility Commission (PUC) adopted rules requiring each electricity provider to supply at least 30% of their total electric sales using electricity generated from eligible renewable and certain energy efficiency resources. At the time of passage, the required percentage of renewable energy was actually lower than the existing percentage supplied.

Eligible Technologies

Eligible facilities include those up to 100 megawatts (MW) in capacity that use fuel cells, tidal, solar, wind, geothermal, hydro, biomass, or municipal solid waste in conjunction with recycling. Electricity generated by efficient combined heat and power (CHP) facilities and other systems that qualify as "small power production facilities" under the federal Public Utility Regulatory Policies Act of 1978 (PURPA) also are eligible.

Since 1999, the renewable portfolio standard (RPS) has been amended several times and two separate classes designated. Class II includes existing renewables, which are eligible to meet the 30% requirement described above. Class I is composed of new renewables that have come on-line after September 1, 2005. Unlike Class II, municipal solid waste facilities and CHP facilities are not eligible for Class I, and there are more stringent hydropower qualifying requirements. In addition, new wind installations may exceed 100 MW.


The schedule for the Class I standard is as follows:

  • 1% for the period from 1/1/2008 to 12/31/2008
  • 2% for the period from 1/1/2009 to 12/31/2009
  • 3% for the period from 1/1/2010 to 12/31/2010
  • 4% for the period from 1/1/2011 to 12/31/2011
  • 5% for the period from 1/1/2012 to 12/31/2012
  • 6% for the period from 1/1/2013 to 12/31/2013
  • 7% for the period from 1/1/2014 to 12/31/2014
  • 8% for the period from 1/1/2015 to 12/31/2015
  • 9% for the period from 1/1/2016 to 12/31/2016
  • 10% for the period from 1/1/2017 to 12/31/2022

In 2017, Maine extended the 10% Class I requirement to year 2022. 


The PUC has approved the use of NEPOOL Generation Information System (GIS) certificates (which are similar to renewable energy certificates, or RECs) to satisfy the portfolio requirement. GIS certificates are awarded based on the number of kilowatt-hours (kWh) of eligible electricity generated. GIS certificates used to meet the Class I standard may not also be used to satisfy the Class II standard. There is a 1.5 credit multiplier available for qualifying community-based renewable energy projects (see the Community-Based Renewable Energy Production Incentive for more information).

The PUC sets an alternative compliance payment (ACP) that utilities may pay instead of satisfying the standard by procuring GIS certificates. The PUC set the ACP base rate for the Class I standard at $57.12 per megawatt-hour (MWh) in 2007; this rate has been adjusted annually for inflation beginning in 2008. The 2018 ACP rate is $68.87 per MWh. Revenues from ACPs will be directed to the state's Renewable Resource Fund).

Legislation enacted in 2011 (Public Act 413) required the PUC to study the renewable portfolio standard. The results were published in January 2012 in the comprehensive report, MPUC RPS Report 2011 - Review of RPS Requirements and Compliance. Furthermore, the Maine PUC submits an annual report on the status of compliance with the new renewable resources (Class I) portfolio requirement.

Maine Wind Energy Goals

In addition to the standard above, there are three goals for wind energy development in Maine: (1) at least 2,000 MW of installed capacity by 2015; (2) at least 3,000 MW of installed capacity by 2020, of which there is a potential to produce 300 MW from facilities located in coastal waters or offshore; and (3) At least 8,000 MW of installed capacity by 2030, of which 5,000 MW should be from facilities in coastal waters or offshore. The first two goals were established in April 2008 (L.D. 2283), and the third was established in April 2010 (L.D. 1810).  

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