PPA: Power Purchase Agreement. The homeowner agrees to purchase power from the PV system owner for a period of 10-20 years. The homeowner buys electricity at a reduced rate, and the PV system owner earns a return on their investment.

PV: Photovoltaic. This is a solar system that generates electricity, rather than heat. These systems generally require more panels to satisfy a resident's electric needs, compared to a heat or hot water system to satisfy those requirements.

SREC: Solar Renewable Energy Credit. These credits are minted by owners of PV systems for 10 years, and are purchased by utilities to meet state requirements. The credit price varies like a stock since they are traded on a market, but prices are supported by the state.

Sustainable: Living within the carrying capacity of the Earth’s supporting eco-systems, without degrading or depleting any resource that would affect future generations. Generally the measures of sustainability consider economic, environmental, and social conditions, with a goal of reducing inequalities within and among societies.