Solar Term List
From Amps to Zero Export: A Solar Dictionary
Welcome to the Solar ABCs, your plain‑English guide to the language of solar power.
If you’re new to solar, the terminology can feel overwhelming: AC, DC, MPPT, net metering, rapid shutdown. But don’t let the alphabet soup scare you. Every one of these terms describes a simple idea, and once you know the basics, the rest starts to fall into place.
Think of this list as your reference table. Whether you’re comparing quotes from installers, reading a solar invoice, or just trying to understand how a panel turns sunlight into the power that runs your fridge, you’ll find a clear, accurate definition here.
We’ve kept each entry short, practical, and free of unnecessary jargon. From "ampere" to "watt," the words below are the building blocks of every solar conversation.
So bookmark this page, flip to the letter you need, and let’s get you speaking solar confidently!
A
AC Coupling – A wiring method that connects a battery inverter to a grid-tied solar inverter on the AC side. It allows an existing grid-tied solar system to add battery backup without replacing the original inverter.
Alternating Current (AC) – Electric current that periodically reverses direction. In the US, utility power and home appliances use AC at 60 cycles per second (60 Hz). Solar panels produce DC, so an inverter is needed to convert to AC.
Ampere (Amp) – The unit that measures the flow rate of electric current. Think of it like gallons per minute flowing through a pipe. Abbreviation: A.
Amp-Hour (Ah) – A unit of electric charge, often used to rate batteries. One amp-hour means delivering 1 amp of current for 1 hour. A 100 Ah battery can theoretically supply 5 amps for 20 hours.
Amp-Hour Meter – A device that tracks cumulative energy flowing into or out of a battery bank, helping estimate the battery’s state of charge.
B
Battery Box – An enclosure for wet-cell (flooded) batteries. It contains and vents explosive hydrogen gas outside. It also protects batteries from weather in outdoor or remote installations.
Bifacial Solar Panel – A panel that captures sunlight on both its front and rear sides. It produces extra energy when mounted above reflective surfaces like white roofing, sand, or light-colored gravel.
C
Capacity Factor – The actual energy output of a solar system over time divided by its theoretical maximum output if it ran at full power 24/7. For solar, typical values are 15–25%.
Charge Controller – An electronic device that regulates voltage and current from solar panels to properly charge batteries. It prevents overcharging. Systems without batteries (grid-tied only) do not need one.
Combiner Box – A junction box where the output wires from multiple solar panels (or strings) are safely combined into larger feeder wires. Often includes fuses or circuit breakers per input.
D
DC-to-AC Ratio (Sizing Ratio) – The ratio of a solar array’s DC wattage to the inverter’s AC wattage. A ratio of 1.2 (e.g., 6 kW DC on a 5 kW AC inverter) is common to maximize real-world output.
Direct Current (DC) – Electric current that flows in one direction only. Solar panels produce DC, and batteries store DC. Homes and the grid use AC, so DC must be inverted.
E
Energy Audit – A professional assessment of a building’s energy use. It identifies waste and efficiency upgrades. Always do an energy audit before sizing a solar system to avoid oversizing.
F
Fill Factor (FF) – A measure of a solar cell’s quality. It is the ratio of the cell’s actual maximum power to the product of its open-circuit voltage and short-circuit current. Higher is better.
Flooded Batteries – Lead-acid batteries that use liquid distilled water as the electrolyte. They require regular water refills and ventilation. They are the most economical choice for off-grid solar.
G
Grid-Tied (On-Grid) System – A solar power system connected to the public utility grid. It does not need batteries. Excess power is sent to the grid, and grid power is used when solar is insufficient.
Ground Fault – An unintended electrical path from a live conductor to ground. Solar systems require ground fault protection devices (GFPDs) to detect and stop these faults.
H
Hybrid Inverter – An inverter that can manage both solar panels and batteries simultaneously. It can send power to the grid, to home loads, or to/from a battery bank. Hybrid inverters are the backbone of modern solar + storage systems.
I
Inverter – A device that converts DC electricity from solar panels or batteries into AC electricity for home appliances or the grid. Types include string inverters, microinverters, and hybrid inverters.
Islanding – A dangerous condition where a solar inverter continues to power a local circuit after the utility grid shuts down. Modern grid-tied inverters have anti-islanding protection to automatically stop output.
J
Junction Box (J-Box) – An enclosure attached to some solar panels where electrical connections are made. Panels may have a J-box or pre-attached cables (e.g., MC4 connectors).
K
Kilowatt (kW) – 1,000 watts. A measure of power capacity. A typical home solar system might be 5–10 kW in size.
Kilowatt-hour (kWh) – The standard unit of energy for electricity billing. Using 1,000 watts for 1 hour = 1 kWh. A 5 kW solar system producing full power for 5 hours generates 25 kWh.
L
Load – Any device that consumes electricity. Also refers to the total power demand of a site, expressed in kilowatts (capacity) or kilowatt-hours (energy use over time).
M
Maximum Power Point Tracking (MPPT) – An advanced charge controller or inverter feature that continuously adjusts the operating point of the solar array to harvest the maximum available power under changing light and temperature.
Microinverter – A small inverter mounted on each individual solar panel. It converts DC to AC right at the panel, allowing each panel to perform independently. Great for partial shade conditions.
Monitoring System – Software and hardware (often web or app-based) that tracks real-time and historical solar production, consumption, and system health.
Mounting Equipment – Hardware used to attach solar modules to a roof, ground, or pole. Includes rails, clamps, flashing, and tilt legs. Selection depends on roof type, snow/wind loads, and aesthetics.
N
National Electrical Code (NEC) – A US standard for safe electrical installation, updated every 3 years. Article 690 covers solar photovoltaic systems. It is not federal law but is adopted by most local jurisdictions.
Net Metering – A billing arrangement where utility customers with solar get credit for excess electricity they send to the grid. The meter effectively runs backward. Rules vary by state and country.
O
Overcurrent Protection – A safety device (fuse or circuit breaker) that automatically shuts off power if current exceeds a safe level. Required by code for solar systems.
P
Panel Efficiency – The percentage of sunlight striking a solar panel that is converted into electricity. Higher efficiency means more power per square foot. Typical values: 15–22%.
Performance Ratio (PR) – A key quality metric of a solar system. It accounts for real-world losses (temperature, shading, soiling, wiring). PR = actual output / theoretical ideal output. A good system has PR > 0.80.
Polycrystalline Panel – A panel made from multiple silicon crystals. It has a blue, speckled appearance. Slightly less efficient than monocrystalline but more affordable.
Power Optimizer – A module-level power electronics device (often paired with a string inverter). It optimizes DC output per panel but does not convert to AC. Provides panel-level monitoring and rapid shutdown.
Q
Qualified Installer – A certified professional who meets local licensing, training, and safety standards for solar installation. Hiring a qualified installer helps ensure code compliance, safety, and eligibility for rebates and warranties.
R
Rapid Shutdown – A safety requirement (NEC 2017/2020) that reduces voltage in a solar array to safe levels (under 80 volts within 30 seconds) to protect firefighters.
Rebate – A cash incentive from utilities or local agencies paid after solar installation. Usually based on system size in watts. Rebates are less common than tax credits today.
S
Sealed Batteries – Lead-acid batteries that are closed and do not lose electrolyte. No maintenance needed. Types include AGM (Absorbed Glass Mat) and Gel Cell. More expensive than flooded but ideal for indoor or low-maintenance use.
Solar Array – A group of connected solar panels, typically mounted together on a roof, ground frame, or pole.
Solar Cells (Photovoltaic Cells) – The individual semiconductor devices that convert light directly into DC electricity. Most are made of silicon and produce about 0.5 volts each.
Solar Panels (Modules) – Panels made of many solar cells connected in series. Common sizes: 36 cells (~17V, 12V nominal), 60 cells (~20V), 72 cells (~24V).
String – A series of solar panels connected end-to-end (positive to negative) to increase voltage. Multiple strings are combined in a combiner box.
T
Tax Credit – An incentive that directly reduces income tax owed. The US federal Investment Tax Credit (ITC) covers 30% of solar system cost (through 2032). Some states and localities add their own.
Tilt Angle – The vertical angle at which solar panels are mounted relative to horizontal. Optimizing tilt for your latitude increases annual energy yield.
U
Utility Interactive – Another term for a grid-tied solar system. It means the solar inverter can interact with the utility grid, synchronizing to grid voltage and frequency, and shutting down automatically when the grid fails (anti-islanding).
V
Volt (V) – The unit of electrical potential or “force” that pushes current through a circuit. US homes use 120V and 240V. Solar panels typically produce 12V to 50V DC. Formula: volts = watts / amps.
W
Watt (W) – The unit of electrical power. It measures instantaneous rate of energy use or production. A 300W solar panel produces 300 watts at peak. 1,000 watts = 1 kilowatt.
Y
Yield – The total energy produced by a solar power system over a specific period, typically measured in kilowatt-hours (kWh). Annual yield is often compared to the system's rated DC size (specific yield, kWh per kW).
Z
Zero Export – A feature of some solar inverters that prevents power from being sent back to the utility grid. Required in some jurisdictions or for customers with no net metering agreement. Excess generation is curtailed or diverted to batteries or water heaters.