This glossary covers terms you'll see across our solar content, contractor quotes, manufacturer spec sheets, and incentive program documentation. Use it as a reference - we link key terms from across the site back to definitions here.
- Photovoltaic (PV)
- The technology that converts sunlight directly into electricity using semiconductor cells. Residential solar panels are PV modules.
- Kilowatt (kW)
- A unit of power. Residential solar systems are sized in kW - a typical home system is 6-10 kW.
- Kilowatt-hour (kWh)
- A unit of energy. One kW of demand for one hour. Your electric bill measures consumption in kWh.
- Inverter
- Converts DC electricity from solar panels into AC electricity your home uses. Types include string inverters, microinverters, and hybrid inverters.
- Microinverter
- A small inverter installed at each panel, allowing per-panel power optimization. Common brands: Enphase, APsystems.
- Net Metering
- Utility billing system that credits solar owners for excess electricity exported to the grid.
- Net Energy Metering 3.0 (NEM 3.0)
- California's current net metering policy, replacing NEM 2.0 in 2023. Reduces export compensation but encourages battery storage.
- Federal Investment Tax Credit (ITC)
- 30% federal tax credit for residential solar installations under Section 25D of the IRS code, available through 2032.
- Solar Renewable Energy Certificate (SREC)
- A tradable certificate representing 1 MWh of solar generation. Some states have SREC markets (or successor programs like NJ SuSI).
- SuSI (Successor Solar Incentive)
- New Jersey's replacement for SREC. Pays a fixed per-kWh incentive for 15 years.
- Peak Sun Hours
- Average hours per day of full-strength sunlight at a given location. Most US locations get 4-6 peak sun hours per day.
- Tilt and Azimuth
- Tilt = angle of panels from horizontal. Azimuth = compass direction panels face. South-facing with tilt equal to latitude is optimal in the US.
- Solar Loan
- A loan specifically for financing residential solar. Allows you to claim the ITC since you own the system.
- Power Purchase Agreement (PPA)
- Contract where the solar company owns the system on your roof and you buy the electricity at a fixed rate. You don't claim the ITC.
- Solar Lease
- Similar to a PPA - the installer owns the panels and you pay a monthly lease for use. No ITC for you.
- Interconnection
- The utility process of approving and connecting your solar system to the grid.
- Permission to Operate (PTO)
- Final utility approval that lets you turn your solar system on after installation and inspection.
- Solar Battery
- Stores excess solar production for use at night or during outages. Common: Tesla Powerwall, Enphase IQ Battery.
- Time-of-Use (TOU) Rates
- Utility rate structure where electricity prices vary by time of day. Solar+battery is especially valuable under TOU rates.
- Critical Load Panel
- A secondary electrical panel that batteries can keep powered during outages, isolating essential circuits.
- DC-Coupled vs AC-Coupled
- How battery storage connects to solar. DC-coupled is more efficient for new installs; AC-coupled works for retrofits.
- Solar Production Estimate
- Annual kWh your system will produce, based on system size, tilt, azimuth, and shading. Used to estimate payback.
- Solar Payback Period
- Years until cumulative electricity savings + incentives equal system cost. Typical residential payback: 6-12 years.
- Module Level Power Electronics (MLPE)
- Per-panel optimization devices (microinverters or DC optimizers). Required by NEC for rapid shutdown.
- Rapid Shutdown
- Safety requirement that lets first responders quickly de-energize a rooftop solar system.