EV & energy glossary
50key terms across EV charging, electrical code, heating & cooling, energy, and finance — explained in plain English.
EV Charging
- Level 1 charging
- Charging from a standard 120-volt household outlet at about 1.2–1.4 kW, adding roughly 3–5 miles of range per hour. No installation needed. Learn more →
- Level 2 charging
- Charging from a dedicated 240-volt circuit at about 7.2–11.5 kW, adding roughly 20–40 miles of range per hour. Needs an electrician to install. Learn more →
- DC fast chargingDCFC
- High-power direct-current charging (about 50–350+ kW) found at public stations. Typically takes an EV from 10% to 80% in 20–40 minutes, then slows sharply. Learn more →
- Kilowatt-hourkWh
- A unit of energy — what your battery holds and what you're billed for. A 60 kWh battery stores 60 kilowatt-hours. Learn more →
- KilowattkW
- A unit of power — how fast energy flows. Charging power (kW) determines how quickly the battery fills.
- State of chargeSoC
- How full the battery is, as a percentage. Charging and range estimates are based on the change in state of charge.
- NACS (J3400)
- North American Charging Standard — the Tesla connector, now standardized as SAE J3400 and adopted industry-wide. Handles AC and DC over one plug. Learn more →
- J1772
- The standard US AC connector for Level 1 and Level 2 charging on non-Tesla EVs. Learn more →
- CCS (Combined Charging System)CCS1
- A J1772 connector with two added DC pins for fast charging — the common DC standard on many non-Tesla US EVs.
- CHAdeMO
- An older DC fast-charge connector (e.g. early Nissan Leaf), now being phased out in North America.
- Onboard charger
- The AC charger built into the car. It caps Level 2 speed — a higher-power wall unit won't charge faster than the onboard charger accepts.
- EVSE
- Electric Vehicle Supply Equipment — the technical name for the 'charger' (the wall unit or cord that supplies power to the car).
- Charging losses
- Energy lost as heat during charging. AC home charging is typically 85–90% efficient, so you pay for slightly more energy than reaches the battery.
- Efficiency (mi/kWh)
- How far an EV travels per kilowatt-hour. Typical EVs do 3–4 mi/kWh; efficient sedans exceed 4, large trucks may be 2–2.5. Learn more →
Electrical (NEC)
- Ampereamp / A
- The unit of electric current — the rate of electricity flow. Breakers and circuits are rated in amps.
- VoltV
- The unit of electrical potential. US homes use 120V for general outlets and 240V for large loads like dryers, ranges, and EV chargers.
- WattW
- The unit of power. Watts = volts × amps. 1,000 watts = 1 kilowatt (kW). Learn more →
- Circuit breaker
- A switch that automatically cuts power if current exceeds its rating, protecting the wiring from overheating. Standard sizes are set by NEC 240.6.
- National Electrical CodeNEC / NFPA 70
- The US standard for safe electrical installation. Adopted (often with amendments) by states and enforced by the local authority.
- American Wire GaugeAWG
- The US system for conductor size. Lower numbers are thicker wire that carries more current (e.g. 6 AWG > 8 AWG). Learn more →
- Ampacity
- The maximum current a conductor can carry continuously without overheating, per NEC Table 310.16. Depends on wire size, insulation temperature rating, and conditions. Learn more →
- Continuous load
- A load expected to run for 3 hours or more (like EV charging). The NEC requires its circuit to be rated for 125% of the load.
- 125% rule
- For continuous loads, the breaker and wire must be sized to 125% of the load. A 40-amp EV charger needs a 50-amp breaker (40 × 1.25). Learn more →
- GFCI
- Ground-Fault Circuit Interrupter — a device that quickly cuts power on a ground fault to prevent shock. Required for EV supply equipment and many 240V receptacles.
- Service / panel
- Your home's main electrical supply and breaker box. Common residential sizes are 100, 150, 200, and 400 amps. Learn more →
- Load calculation
- The NEC Article 220 method for totaling a home's electrical demand using demand factors, to see if the service can handle a new load. Learn more →
- Authority Having JurisdictionAHJ
- The local official or office that enforces the electrical code, issues permits, and inspects work. The AHJ can amend the NEC and has the final say.
- NEMA 14-50
- A 240-volt, 50-amp receptacle (used for ranges and RVs). A plug-in EV charger on one is limited to a 40-amp continuous draw. Learn more →
Heating & Cooling
- Heat pump
- A system that moves heat rather than creating it, delivering 2–4 units of heat per unit of electricity. Reverses to cool in summer. Learn more →
- Coefficient of PerformanceCOP
- Heat delivered per unit of energy used. Electric resistance heat has a COP of 1.0; a heat pump runs at a seasonal COP of about 2.5–4.0. Learn more →
- SEER2
- Seasonal Energy Efficiency Ratio (2023 update) — a cooling efficiency rating. Higher is more efficient.
- HSPF2
- Heating Seasonal Performance Factor (2023 update) — a heating efficiency rating for heat pumps. Higher is more efficient.
- British Thermal UnitBTU
- A unit of heat energy. Heating and cooling capacity is rated in BTU per hour.
- Ton
- A unit of cooling/heating capacity. One ton = 12,000 BTU per hour. Learn more →
- Manual J
- The ACCA standard load calculation that sizes heating and cooling equipment based on the home's heat gain and loss — the right way to size a system. Learn more →
- AHRI
- The directory that publishes verified performance ratings for matched HVAC systems. ENERGY STAR identifies qualified efficient models.
- AFUE
- Annual Fuel Utilization Efficiency — the seasonal efficiency of a fuel-burning furnace (e.g. 0.92 = 92% of the fuel's energy becomes heat).
- Ductless mini-split
- A heat pump with no ductwork — an outdoor unit feeds one or more wall-mounted indoor heads. Good for homes without ducts or for zoning. Learn more →
Energy & Generators
- Residential electricity rate
- The price you pay per kilowatt-hour ($/kWh), from your utility bill. It varies widely by state, from around 11¢ to over 40¢. Learn more →
- Time-of-useTOU
- A rate plan where the price per kWh changes by time of day. Charging or running appliances off-peak lowers the cost.
- Demand factor
- A NEC allowance recognizing that large loads rarely all run at once, so the calculated demand is less than the sum of nameplate ratings.
- Running watts
- The continuous power an appliance draws while operating. Add these up for everything you'll run at once. Learn more →
- Starting (surge) watts
- The brief power spike when a motor starts — often 2–3× its running watts. A generator must cover running watts plus the largest single surge. Learn more →
- Transfer switch
- The device that safely connects a generator to your home's circuits. Standby units use an automatic transfer switch; portables need a manual one or an interlock — never back-feed an outlet.
Finance
- Annual Percentage RateAPR
- The yearly interest rate on a loan. A higher APR or longer term raises the total interest you pay. Learn more →
- Total Cost of OwnershipTCO
- The full cost of owning a vehicle over time — purchase price plus fuel, maintenance, and other running costs — not just the sticker price. Learn more →
- Payback period
- How long it takes for the savings from a purchase (like a heat pump or EV) to repay its higher upfront cost. Learn more →
- Break-even point
- The moment cumulative savings equal the extra amount you paid upfront — after which you're ahead. Learn more →
- Amortization
- Paying off a loan in equal installments over a set term, where each payment covers interest plus a portion of the principal.
- Point-of-sale credit
- An incentive (like an EV tax credit) applied at purchase to reduce the amount you finance — which also lowers the interest you pay versus claiming it later. Learn more →
Put the terms to work
Try the calculators, read the guides, or browse more reference charts.