Solar Glossary: A-Z Terms Every Homeowner Should Know

A

AC (Alternating Current): The form of electricity used in your home. Solar panels produce DC; an inverter converts it to AC.

AC coupling: A battery storage architecture where solar panels connect to their own PV inverter, and the battery has a separate inverter that taps in on the AC side. Best for retrofitting storage onto existing solar. Round-trip efficiency typically 88–92%. See battery storage guide.

Amortization: The schedule of how a loan is paid down over time. Solar loans typically amortize over 10–25 years.

Array: The full collection of solar panels installed on your roof or property.

Avoided cost rate: The wholesale rate utilities pay for excess solar exports under net billing structures. Typically 3–8 cents/kWh — far below retail. See net metering explained.

Azimuth: The compass direction your panels face. South = 180° (best in the Northern Hemisphere). East = 90°, West = 270°.

B

Backup Gateway / Backup Reserve: Tesla's hardware (Backup Gateway) and software setting (Backup Reserve %) that handle utility disconnect during outages and reserve battery capacity for emergencies.

Battery storage: A home battery that stores excess solar production for use later (overnight, during outages, or when rates are higher). Common brands: Tesla Powerwall, Enphase IQ Battery, FranklinWH, EG4. See battery storage guide.

Bifacial panel: A solar panel that captures light on both sides. Useful for ground mounts; minimal benefit for rooftop installs.

BMS (Battery Management System): Embedded electronics in a battery that monitor cell voltages, temperatures, and balance the pack. Required for safe operation of any lithium battery.

BOS (Balance of System): Everything in a solar system that isn't the panels — inverters, racking, wiring, monitoring, etc.

C

CAN bus: A communications protocol (Controller Area Network) used between modern hybrid inverters and batteries for closed-loop integration. Faster and more capable than older RS485/Modbus links.

Capacity factor: Actual energy produced divided by theoretical maximum. Residential solar is typically 15–22% capacity factor.

Charge on Solar: Tesla feature (and similar features in Wallbox, Enphase EV chargers) that dials EV charging up and down to match real-time PV production. Useful in NEM 3.0 / net billing states.

Clipping: When solar panels produce more DC power than the inverter can convert to AC. Some clipping is intentional with DC/AC oversizing — see inverter guide.

Closed-loop battery protocol: Real-time CAN bus communication between an inverter and a specific approved battery model — gives the inverter accurate state-of-charge data and enables intelligent charge/discharge logic. Contrast with open-protocol setups where the inverter only knows voltage.

Commercial ITC (Section 48E): The federal Investment Tax Credit for business-owned solar. Available in 2026 for third-party-owned residential systems (lease/PPA) — the installer claims it and may pass savings through to your monthly payment.

Continuous output: The kW a battery or inverter can deliver indefinitely. Different from surge rating, which is what it can deliver for ~10 seconds during motor starts.

Cost per watt ($/W): Total system price divided by system size in watts. The best metric for comparing solar bids. See $/W guide.

Critical loads subpanel: A separate breaker panel containing only the circuits you want backed up during an outage. Used when battery capacity isn't enough for whole-home backup.

Daily kWh need: Sum of (load wattage × hours per day) for all backed-up loads. Used in battery sizing. Add 25% safety margin to size capacity.

Demand charge: A separate $/kW charge on commercial utility bills based on the highest 15-minute peak draw during the billing period. Solar without storage doesn't reduce demand charges; solar + battery does. See utility bill analyzer.

Distributor: Wholesale supplier that sells solar equipment to installers (CED Greentech, Soligent, Krannich, Renvu, BayWa r.e.). See equipment vendors.

DC (Direct Current): The form of electricity solar panels produce. Converted to AC by an inverter.

Detach & Reset (D&R / R&R): Removing existing solar panels for a roof replacement and reinstalling them after the new roof is on. In Minnesota typically $350–$850 per panel depending on roof pitch and lift requirements. See detach & reset guide.

DC/AC ratio: The ratio of installed DC panel capacity to AC inverter rating. Typical 1.10–1.50:1. Higher ratios increase production in real-world conditions.

DC coupling: A battery storage architecture where solar panels connect directly to a hybrid inverter that also manages the battery. Round-trip efficiency typically 92–96%. Best for new installs where solar and storage are designed together. See hybrid inverter guide.

Dealer fee: The hidden markup baked into financed solar pricing to subsidize a low APR. Often 20–35% of the cash price.

Degradation: The gradual decline in solar panel output over time. Premium panels: 0.25–0.4%/year. Budget: 0.5–0.7%/year.

Depth of Discharge (DoD): The percentage of a battery's nameplate capacity that's actually usable. Modern LFP batteries typically allow 95–100% DoD.

E

Efficiency: Percentage of sunlight a panel converts to electricity. Modern residential panels: 19–22.8%.

Escalator: The annual percentage increase in lease or PPA payments. Typical 1.9–3.9%. Demand 0% if signing a lease.

Essential loads: The circuits you'd want to keep running during a power outage — typically refrigerator, lights, internet, well pump, and a few outlets. Often wired into a critical loads subpanel.

EVSE (Electric Vehicle Supply Equipment): The technical name for an "EV charger." Common Level 2 brands: Tesla Wall Connector, Wallbox, ChargePoint, Enphase IQ EV Charger. See solar + EV charging.

Export: Excess solar production sent back to the utility grid.

F

Feed-in tariff (FIT): A separate fixed dollar amount paid per kWh exported, typically higher than retail. Common in Europe; rare in the U.S.

Fixed connection fee: Monthly utility charge that applies regardless of usage. $10–$30 in most states. You still pay this with solar.

FranklinWH: Manufacturer of the aPower 2 home battery and aGate energy management controller. 15 kWh in a single unit, 15-year warranty, native generator integration.

G

Generator integration: A hybrid inverter feature that auto-starts a backup generator when battery state of charge drops below a threshold, then shuts it back off after recharging. Reduces required generator size dramatically. See hybrid inverter guide.

Grid-tied: A solar system connected to the utility grid (the standard setup). Allows net metering and grid backup.

Ground mount: Solar panels mounted on the ground rather than on a roof. Useful when roof isn't suitable. See roof suitability.

H

HelioScope: A common shading and production analysis software. If your proposal includes a HelioScope report, that's a good sign.

Hybrid inverter: An inverter that combines PV input, battery management, grid interface, and generator integration in one unit. Sol-Ark and EG4 dominate the residential hybrid market in 2026. See hybrid inverter guide.

I

Interconnection: The utility approval process for connecting your solar system to the grid. Typically takes 30–90 days after install.

Inverter: The device that converts DC from panels to AC for your home. See inverter comparison.

Irradiance: Solar energy hitting a surface, measured in W/m². Determines how much your panels can produce.

ITC (Investment Tax Credit): The federal credit for business-owned solar (Section 48E). Available in 2026 for lease and PPA financing structures, where the installer claims it and may pass savings through. Also see federal tax credit guide.

K

kW (kilowatt): A unit of power. System sizes are typically expressed in kW (e.g., 8 kW system).

kWh (kilowatt-hour): A unit of energy. Your utility bill measures usage in kWh. 1 kW running for 1 hour = 1 kWh.

kWh/kW/year (specific yield): How much energy each kW of installed solar produces per year. Range: ~1,000 (Pacific NW) to ~1,700 (Southwest).

L

Lead Aggregator: A website that collects homeowner contact info via a "free quote" form and sells it to installers. Major players: EnergySage (marketplace), SolarReviews (review + lead-sale hybrid), Solar.com, Modernize, HomeAdvisor/Angi. Lead acquisition cost ($25–$300/lead) gets baked into your final bid. See solar lead aggregators guide.

Lease: A solar financing option where a third party owns the system and you pay monthly to use the electricity. Has escalators. See comparison.

Levelized Cost of Energy (LCOE): The total lifetime cost of solar divided by total lifetime production. The best apples-to-apples comparison metric for energy.

Level 1 / Level 2 / Level 3 charging: EV charging speeds. L1 is a 120V outlet (~3–5 mi/hr). L2 is a 240V dedicated circuit (~25–45 mi/hr) — what most homeowners install. L3 is DC fast charging (commercial only).

LFP (Lithium Iron Phosphate): The dominant battery chemistry for residential storage in 2026. Safer, longer-cycling, and now cheaper than NMC. All major home batteries (Powerwall 3, IQ Battery 5P, Franklin aPower, EG4-LL) use LFP.

Locked rotor amps (LRA): The brief peak current draw when a motor starts (well pumps, AC compressors). Used to spec inverter surge ratings for off-grid and backup designs.

M

Microinverter: A small inverter attached to each panel. Better for shaded/complex roofs. Enphase IQ8 is the dominant brand.

Modbus: An older communications protocol still used between some inverters and batteries. Open and well-documented, but slower than CAN bus.

Module: Industry term for a solar panel.

Monitoring: Software showing your system's real-time and historical production. Microinverters and DC optimizers provide per-panel monitoring.

MPPT (Maximum Power Point Tracking): Inverter circuitry that constantly adjusts voltage to extract peak power from a panel string under varying conditions. More MPPTs = more flexibility for roofs with multiple orientations or shading.

N

NABCEP: North American Board of Certified Energy Practitioners. The industry standard certification for solar installers.

Net billing: A successor structure to net metering where exports are credited at avoided-cost rates (much lower than retail) while imports are billed at full retail. The dominant new-customer structure in CA, HI, AZ, and others. See net metering explained.

Net metering: Utility policy that credits you for excess solar production at retail rates. The most favorable structure for solar economics.

NEM 3.0: California's net billing successor to net metering, effective April 2023. Cut export credits by ~75%.

NMC (Nickel Manganese Cobalt): An older lithium battery chemistry, still used in some EVs. Largely replaced by LFP in residential storage due to fire risk and shorter cycle life.

NREL: National Renewable Energy Laboratory. Maintains PVWatts, the gold-standard production calculator.

O&M (Operations & Maintenance): Ongoing care of a solar/battery system — visual inspection, monitoring review, inverter cleaning, panel rinsing in dry climates, firmware updates, tree trimming. See O&M guide.

Off-grid days: Number of days a battery system can sustain selected loads without grid or solar recharge. Used in battery sizing for outage-prone areas.

Offset: The percentage of your annual electricity usage your solar system is sized to produce. 100% offset doesn't mean $0 bill. See offset guide.

Open battery protocol: A published-specification communication standard (often Modbus) that lets multiple battery brands work with a given inverter. Common with Sol-Ark and EG4 hybrid inverters.

Optimizer (DC optimizer): A small device on each panel that allows independent operation with a string inverter. SolarEdge is the dominant brand.

P

Pass-through current: The maximum current a hybrid inverter can route between the grid and the home's main panel without converting it. EG4 18kPV has 200A pass-through, allowing whole-home backup without a critical-loads subpanel.

Payback period: Years for solar savings to equal net cost. National 2026 average: ~12 years for cash. See payback guide.

Pitch (roof): The angle of the roof slope. 15–45° works well for solar. Flat roofs need tilted racking. See roof suitability.

PPA (Power Purchase Agreement): A solar contract where you pay $/kWh for power produced. Similar to a lease but pay-per-production.

PTO (Permission to Operate): Final utility approval to turn your solar system on. The official "in service" date.

PVWatts: Free NREL tool for estimating solar production. The industry-standard validation tool.

RMA (Return Material Authorization): Formal warranty-claim process to replace a defective panel, inverter, or battery. Each manufacturer has its own RMA portal and documentation requirements. See RMA guide and manufacturer contacts.

Racking: The metal framework that mounts solar panels to your roof. Common brands: IronRidge, Unirac, SnapNrack.

Rapid shutdown: NEC-required safety feature that de-energizes panels during emergencies. Microinverters/optimizers comply natively.

Re-amortization: When a loan recalculates payment based on remaining principal. Older solar loans assumed a tax credit paydown — now a payment-shock risk.

Round-trip efficiency: Percentage of energy stored in a battery that can be recovered when discharged. DC-coupled storage: 92–96%. AC-coupled: 88–92%.

Self-consumption: Using your own solar production directly rather than exporting it to the grid. Critical in net-billing states (NEM 3.0, AZ RCP, IN EDG) where exports earn far less than retail rates.

Surge load: Brief power spike (typically 10 seconds) when motor-driven appliances start — AC compressors, well pumps, sump pumps, refrigerators. 3–7x running wattage. Battery / inverter must handle the surge or the appliance won't start. See battery sizing tool.

SEG Solar: Houston-based solar panel manufacturer with US production in Texas. Mid-market option with strong domestic-content compliance.

Self-consumption: Using your own solar production directly rather than exporting it to the grid. Critical in net billing states where exports earn far less than retail rates.

SGIP (Self-Generation Incentive Program): California rebate program for residential and commercial battery storage. Up to $1,000/kWh for low-income or wildfire-zone homeowners; smaller amounts for general residential.

Shading analysis: A study of how shadows affect your roof. A real proposal includes one (HelioScope, Aurora, Solar Pathfinder).

SMART: Massachusetts solar incentive program with performance-based payments.

Solar shingles: Roofing material that doubles as PV — Tesla Solar Roof, GAF Energy Timberline Solar, CertainTeed Apollo II. Higher cost per watt than traditional panels, but the panels are the roof.

SREC (Solar Renewable Energy Certificate): Tradable certificate for each MWh produced. Valuable in NJ, MD, MA, DC, OH, IL, PA.

STC (Standard Test Conditions): Lab conditions used to rate panel output. Real-world output is typically 80–90% of STC.

String inverter: A central inverter connected to a series of panels. Cheapest option, allows aggressive DC/AC oversizing.

Surge rating: The kW an inverter or battery can deliver for a brief period (typically 10 seconds) during motor startup. Critical for backing up well pumps and AC compressors.

T

Tier 1 panel: Loose marketing term for "reputable manufacturer." Not a meaningful technical spec — always check the actual model and warranty.

Tilt: The angle of your solar panels relative to horizontal. Typically matches roof pitch on rooftop installs.

TOU (Time-of-Use) rate: A utility rate plan where price varies by hour. Evening peak rates are highest, midday lowest. Batteries shift solar production from cheap midday to expensive evening, capturing the rate spread.

True-up: Annual settlement of net metering credits. If you over-produced, you may get a small payment; if under, you owe the balance.

TSRF (Total Solar Resource Fraction): Percentage of ideal solar a roof receives, accounting for shading and orientation. 90%+ is ideal, below 75% is poor.

Two-wire start: Generator interface protocol where the inverter triggers gen start/stop with a simple low-voltage signal. Standard on Sol-Ark and EG4 hybrid inverters.

U

UL 1741 SB: The grid-interaction safety listing required for inverters and energy storage in the U.S. as of 2026.

UL 9540: The system-level safety listing required for residential energy storage systems. Covers fire propagation, ventilation, and installation clearances.

Usable capacity: The kWh of a battery actually available to discharge, after accounting for depth-of-discharge limits. Always compare batteries on usable kWh, not nameplate.

Utility rate: The price you pay per kWh. Higher rates = faster solar payback. Use your marginal rate (not average) for accurate calculations.

V

V2H / V2G (Vehicle-to-Home / Vehicle-to-Grid): Bidirectional charging from compatible EVs (Ford F-150 Lightning, Kia EV9, Hyundai Ioniq 5/9, GM Silverado EV). Lets the EV substitute for or supplement a stationary home battery.

Virtual net metering: A program (available in CA, NY, MA, IL, MN and others) that lets a single solar array's credits be allocated across multiple meters or accounts.

W

Warranty (product): Covers panel manufacturing defects. Typically 12–25 years.

Warranty (performance): Guarantees panel output won't drop below a certain threshold (usually 80–87%) over 25 years.

Warranty (workmanship): Covers installation quality. 10 years minimum from reputable installers; 25 years from top-tier installers.

Watt: Basic unit of power. 1 kW = 1,000 watts. Solar panels are typically 350–450W each.

Whole-home backup: A battery + inverter configuration that backs up a home's full main panel during an outage, vs. a partial-backup design that only powers a critical-loads subpanel. Usually requires 200A pass-through (EG4 18kPV) or multiple batteries (Powerwall 3 ×2).

Frequently asked questions