Electrical terms like Voc, C-rate and split phase come up again and again when you shop for solar panels, batteries and inverters, and this glossary defines them the way the U.S. Department of Energy and the National Electrical Code use them. Bookmark it and come back whenever a spec sheet stops making sense. Each term links to a deeper guide in our Electricity Basics series where one exists.
Basic Electrical Terms
- Volt (V): electrical pressure
- Amp (A): rate of current flow
- Watt (W): rate of power, volts × amps
- Ohm (Ω): resistance
- Watt-hour (Wh) / kWh: energy over time; 1 kWh = 1,000 Wh
- Amp-hour (Ah): charge capacity; multiply by voltage for Wh
- AC / DC: alternating / direct current
- Hz: cycles per second (60 Hz in the US)
- Power factor: real watts ÷ volt-amps
- VA: apparent power, volts × amps
Wiring and Protection Terms
- AWG: American Wire Gauge; lower number = thicker wire
- Ampacity: current a wire can carry safely
- Voltage drop: voltage lost along a wire
- Fuse / breaker: overcurrent protection
- GFCI: protects people from shock
- AFCI: protects against arc fires
- Neutral: normal return conductor
- Ground (EGC): fault path to trip breakers
- Bonding: joining neutral and ground at one point
- Split phase: two 120V legs giving 240V
- Bus bar: common connection bar
- Disconnect: switch that isolates a circuit
Battery Terms
- LiFePO4 (LFP): lithium iron phosphate chemistry
- NMC: nickel manganese cobalt lithium chemistry
- BMS: battery management system
- SoC: state of charge
- DoD: depth of discharge
- C-rate: current relative to capacity
- Cycle life: number of cycles to a set capacity loss
- Throughput: total energy over a battery’s life
- Shunt: precise current sensor for battery monitors
- Absorption / float: charging stages
- Nominal voltage: rated average voltage (12.8V for LFP 12V)
Solar Terms
- STC: standard test conditions
- Voc / Vmp: open-circuit / max-power voltage
- Isc / Imp: short-circuit / max-power current
- Temperature coefficient: change per °C
- MPPT / PWM: charge controller types
- String: panels wired in series
- Irradiance: sunlight intensity, W/m²
- Peak sun hours: daily solar energy expressed as hours at 1,000 W/m²
- Degradation: yearly output loss
- Rapid shutdown: NEC rule to de-energize rooftop arrays
Inverter and Grid Terms
- Inverter: DC to AC
- Inverter-charger: inverter plus battery charger and transfer switch
- Pure sine wave: clean AC output
- Surge: short peak power rating
- Idle draw: power used with no load
- Grid-tie: feeds the utility grid
- Hybrid inverter: solar, battery and grid in one
- Microinverter: one small inverter per panel
- AC / DC coupling: where a battery connects
- Net metering / net billing: how exports are credited
- NEM 3.0: California’s net billing tariff
- Interconnection: utility approval to connect
- PTO: permission to operate
- Transfer switch / interlock: keeps backup power off the grid
- Critical loads panel: subpanel for backed-up circuits
- ESS: energy storage system
- TOU: time-of-use rates
- AHJ: authority having jurisdiction
Electrical Terms Explained With Examples
Some terms make more sense with numbers. Illustrative examples:
| Term | Example | What it shows |
|---|---|---|
| Watts | 120V × 10A = 1,200W | Power is volts times amps |
| kWh | 1,200W for 2 hours = 2.4 kWh | Energy is power times time |
| Amp-hours to Wh | 100Ah × 12.8V = 1,280Wh | Battery capacity in energy terms |
| C-rate | 50A from a 100Ah battery = 0.5C | Current relative to capacity |
| DoD | 80Ah used of 100Ah = 80% DoD | How deeply a battery is cycled |
| Power factor | 840W ÷ 1,200VA = 0.7 | Real vs apparent power |
| Voltage drop | 0.38V lost on a 12.8V run = 3% | Wire loss as a share of voltage |
| Ohm’s law | 12V ÷ 4Ω = 3A | Resistance sets current |
Deeper guides: volts, amps and watts, what is a kilowatt-hour, battery C-rating and VA vs watts.
Electrical Terms and Symbols
| Symbol | Meaning | Where you see it |
|---|---|---|
| V⎓ | DC voltage | Multimeter dial, battery labels |
| V~ | AC voltage | Multimeter dial, appliance labels |
| Ω | Ohms (resistance) | Multimeter dial |
| ⏚ | Ground | Wiring diagrams, equipment terminals |
| + / − | Positive / negative | Batteries, DC terminals |
| Hz | Hertz (cycles per second) | Inverter and appliance labels |
| ⧈ (square inside a square) | Double insulated (Class II) | Tools and chargers with two-prong plugs |
| kW / kWh | Kilowatt / kilowatt-hour | Inverter ratings / bills and batteries |
Abbreviations on Labels and Spec Sheets
| Abbreviation | Stands for | Meaning |
|---|---|---|
| NEC | National Electrical Code (NFPA 70) | US wiring rules, adopted locally |
| UL | UL Solutions (listing mark) | Product tested to a safety standard |
| CAT III / IV | Measurement category (IEC 61010) | Where a meter can be used safely |
| IP65 | Ingress protection rating | Dust-tight, protected against water jets |
| NEMA 5-15, 14-50 | NEMA plug configurations | Plug and receptacle shapes |
| MCA | Minimum circuit ampacity | Smallest wire ampacity for HVAC equipment |
| MOCP | Maximum overcurrent protection | Largest breaker for HVAC equipment |
| RLA / LRA | Rated load / locked-rotor amps | Compressor running and startup current |
| FLA | Full-load amps | Motor current at rated load |
| STC / NMOT | Standard test conditions / nominal module operating temperature | Solar panel rating conditions |
| OCPD | Overcurrent protective device | A fuse or breaker |
| EGC / GEC | Equipment grounding conductor / grounding electrode conductor | Ground wire / wire to the ground rod |
Electrical Terms for Dummies: Five to Learn First
If you only learn five, make it these:
- Watts tell you how much power something uses right now.
- Watt-hours tell you how much energy it uses over time, and how much a battery holds.
- Volts have to match between a device and its power source.
- Amps decide how thick the wire and how big the fuse need to be.
- Usable capacity tells you what a battery really delivers.
Everything else in this glossary builds on those five. The Electricity Basics guide walks through them in order.
Terms That Are Easy to Mix Up
| Pair | Difference |
|---|---|
| kW vs kWh | Power at a moment vs energy over time |
| Ah vs Wh | Charge at one voltage vs energy that compares across voltages |
| Grounding vs bonding | Connecting to earth vs joining metal parts and neutral at one point |
| Neutral vs ground | Normal return path vs fault path |
| Fuse vs breaker | One-time device vs resettable switch |
| GFCI vs AFCI | Shock protection vs arc-fire protection |
| Voc vs Vmp | No-load voltage vs operating voltage at max power |
| Surge vs continuous | Seconds-long peak vs sustained rating |
| VA vs W | Apparent vs real power |
| Series vs parallel | Voltages add vs amp-hours add |
| Net metering vs net billing | Credit at retail rate vs at a lower export rate |
| Nominal vs usable | Label capacity vs what the system lets you use |
See grounding vs bonding and series vs parallel wiring.
Electrical Terms in Spanish
For bilingual shoppers and crews, a few common equivalents:
| English | Spanish |
|---|---|
| Voltage | Voltaje (tensión) |
| Current | Corriente |
| Wire | Cable |
| Ground | Tierra |
| Breaker | Interruptor automático (breaker) |
| Fuse | Fusible |
| Battery | Batería |
| Solar panel | Panel solar |
| Inverter | Inversor |
| Charge controller | Controlador de carga |
FAQ
What’s the difference between kW and kWh?
kW is power at a moment; kWh is energy over time.
Which electrical terms matter most for buying a battery?
Usable kWh, continuous output (kW), chemistry, cycle life and warranty.
Where can I learn more?
Start with our Electricity Basics hub guide.
What is the difference between voltage and current?
Voltage is the pressure that pushes current. Current is the flow, measured in amps.
What are the basic electrical terms?
Volts, amps, watts, ohms, watt-hours, AC and DC cover most of what you’ll see.
What does nominal voltage mean?
The rated average voltage, such as 12.8V for a 4-cell LiFePO4 battery.
Sources: U.S. Department of Energy, “How Does Electricity Work?”; NFPA 70 (NEC) 2023; IEC 61010; NEMA WD 6. Accessed Oct 2026.
Related: Proster Smart Multimeter Review, SunSwift 60A MPPT Solar Charge Controller Review