Solar Terminology


  • Annual kWh – the amount of energy (kWh) used or produced during a one year period. When sizing a PV system, the PV system production must be lower than the previous 12 months of energy use. Ask to see the CSI EPBB reports showing how many kWh the system is estimated to produce when considering solar and doing your cost analysis.
  • Array – several solar modules tied together to form a single structure or group
  • Azimuth – solar system position with respect to the cardinal directions of north, south, east, west, measured in degrees; all references with PV are based on true, not magnetic, azimuth. This is an important factor in solar system energy production.
  • BIPV – Building Integrated Photovoltaics, PV that is part of the building construction rather than being added to the structure later, such as a solar roof tile.
  • CEC AC watts – the system that wattage rebates are based on; includes PTC, inverter efficiencies, and installation characteristics of the array.
  • CO2 – Carbon Dioxide, a well-known Green House Gas, usually referred to when talking about your “Carbon Footprint”.
  • CSI – California Solar Initiative authorized by the California Public Utility Commission is the key component of the Go Solar California campaign for California and rebate program for the Investor Owned Utilities. Roseville Electric’s rebate program is separate from the CSI program but is based on the key components and calculators offered.
  • Electric Panel – the electrical distribution board where the main breaker and branch breakers that feed the home are located.
  • Electric Utility – means Roseville Electric.
  • EPBB (Expected Performance Based Buy-down) – pays an upfront incentive for installing a business customer's solar system of less than 10kW, or a residential solar system; payment is based on the CSI’s CEC-AC watt rating.
  • Grid-connected / Grid-tied – an energy producing PV system which is connected to the electric utility.
  • Inverter – a device that is installed to electronically convert Direct Current (DC) power into Alternating Current (AC) power required for your home's energy using equipment and for grid connected solar systems. These may be central inverters, string inverters, or micro inverters. Insolation – a measure of solar radiation energy, expressed in watt hours per square meter per day. Higher is better for solar system installation energy production.
  • Interconnection – the link connecting the customer and Roseville Electric for electric power flow; an interconnection agreement with Roseville Electric is required by all solar customers.
  • kWh – kilowatt-hours, describes the amount of energy a 1000 watt load operated for a period of one hour. This term is used when estimating energy use and a solar system's expected annual energy production. kW – kilowatt, a unit of power equal to 1000 watt load, which is the designation used for electrical demand. This is also used in sizing solar systems. The system size may be reflected in DC or AC watts.
  • Module – is the solar panel.
  • Net Meter – is an electrical meter that allows power to flow both to and from the home; if the solar system produces more energy than the home needs, the meter will record backwards energy flow.
  • PBI (Performance Based Incentives) – incentive payments for business solar systems 10kW CEC-AC watts or larger; paid on a quarterly basis for a given length of time for measured energy production.
  • Power Purchase Agreement – is an agreement where the customer purchases energy at a set price per kWh, possibly with annual price escalations; the energy in this type of contract is generated and consumed on the customer's site; and the PPA provider installs and maintains the PV system typically at no cost to the home owner.
  • PTC DC watts – PVUSA Test Conditions, performance of solar module in real-word conditions as determined by the California Energy Commission (CEC).
  • PV – Photovoltaic. Photo – light; Volt – electrical potential.
  • Rule 21 – Interconnection Agreement, all customers installing a solar system must abide by these rules and regulations prior to connecting a solar system and while the system is connected.
  • Shading – PV cells are very sensitive to shading, even a small amount of shading may drastically reduce energy production, and even small objects like chimneys, telephone poles, vents may affect solar output. Ask your solar contractor about how to place cells to reduce shade on the array.
  • Shading Analysis – is an essential step in PV system design. The solar contractor will use a shading analysis tool to evaluate the site for shading. Each array orientation must have a shading analysis report, and minimal shading is not allowed by Roseville Electric.
  • Stand-Alone PV System – a PV system that is independent, not connected to, the electric utility grid. This type of system is more inclined to include batteries to store excess energy when it is available and this energy may be used later when it is required.
  • STC DC watts – Standard Test Condition, or nameplate rating of the solar module. Contractors often use this number as the system size.
  • Tilt / Pitch – the solar tilt angle of installation of the solar system towards the sun, and one of the key elements to optimize energy production.