Renewable energy

Renewable energy is generated by sources that can be renewed as opposed to sources that can be used only once, such as fossil fuels.

Under Massachusetts state law, a variety of resources qualify as renewable. The primary sources are solar panels, wind turbines, and small hydroelectric projects. The supply of sunlight, wind, and flowing water is not diminished when we “mine” energy from them. In addition, using electricity from renewable sources does not generate air pollution or the gases that cause climate change.

  • Standard provides 100% of your electricity from renewable sources.
  • 100% Green provides 100% of your electricity from renewable sources within the New England region.
  • Basic provides the minimum amount of your electricity from renewable sources required by law.

Renewable energy content detail

Electricity from renewable sources (% of total) Standard 100% Green Basic Eversource's Basic Service
Term Through November 2026 Beginning December 2026 Through November 2026 Beginning December 2026 Through November 2026 Beginning December 2026 Through November 2026 Beginning December 2026
From new renewable sources in the New England region (MA Class I RECs), added by Watertown 5% – 70% 70% – – – –
From wind projects outside of New England (National Wind RECs), added by Watertown 26% 31% – – – – – –
From new renewable sources in the New England region (MA Class I RECs), required by state law 30% 30% 30% 30% 30% 30% 30% 30%
From other clean or renewable sources, required by state law 39% 39% 39% 39% 39% 39% 39% 39%
Total 100% 100% 139%* 139%* 69% 69% 30% 30%

* The Watertown 100% Green option is a 100% MA Class I RECs offering, which means it includes the minimum amount of MA Class I RECs required by law each year (30% in 2026) plus the additional amount needed to reach 100% (70% in 2026). The program’s electricity supplier is also required by state law to purchase RECs from other sources, including sources that are not new, are renewable but not clean, such as waste to energy, or are clean but not renewable, such as nuclear. This purchase must be made even if the total amount of RECs purchased on your behalf exceeds 100% of your electricity use.

What does it mean to buy renewable electricity / what are RECs?

Unless you have a renewable energy system, such as solar panels, plugged directly into your home or office, you cannot purchase the specific electricity that is generated by a renewable energy project. The electricity flowing through the grid is a comingled mix of electricity generated by renewable energy projects as well as electricity generated by burning fossil fuels.

As a result, a separate accounting system has been created to keep track of renewable energy and allow it to be bought and sold. That system uses renewable energy certificates, or RECs. Every time a renewable energy project generates 1 megawatt-hour of electricity, 1 REC is minted. That REC can then be sold. Purchasing a REC gives you, and no one else, the right to say you used the electricity from that renewable energy project.

Anyone who wishes to purchase renewable electricity must then purchase 2 things (these two costs are often bundled together, which is why renewable energy costs a bit more):

  • the electricity itself from the grid
  • RECs that equal the amount of electricity they wish to claim as renewable

You can buy as many RECs as you wish

  • You can buy a small number of RECs so you can say that a part of the electricity you use is from those renewable sources.
  • You can buy enough RECs to exactly equal the amount of electricity you use, so you can say that all of the electricity you use is from those renewable sources.
  • Or you can buy RECs that equal more than the amount of electricity you use.

Buying RECs provides an important source of revenue for renewable energy developers.

Participants in both the Standard and 100% Green options buy more RECs than are required by state law.

What are MA Class I RECs?

MA Class I renewable energy certificates (RECs) are from renewable energy projects located in the New England region that began commercial operation after 1997, generate electricity using any of the following technologies, and meet all other program eligibility criteria:

  • Solar photovoltaic
  • Solar thermal electric
  • Wind energy
  • Small hydropower
  • Landfill methane and anaerobic digester gas
  • Marine or hydrokinetic energy
  • Geothermal energy
  • Eligible biomass fuel*

Purchasing MA Class I RECs supports regional renewable energy businesses and the jobs that go with them.

* Watertown’s supply contract excludes biomass from the voluntary renewable energy purchased through the program.