Generator glossary

Every word we use on this site, in plain English. Words with a dotted underline in our guides link here.

120 V: The standard US household voltage, from one hot leg to neutral. Most outlets, lights and plug-in appliances use it. Learn more
14-50 (RV 50 amp): A 4-prong straight-blade outlet carrying 120/240 V at 50 A (up to 12,000 W). Used for 50 amp RVs, some big generators and EV charging. Learn more
240 V: The voltage across both hot legs of a US home's supply. Well pumps, electric water heaters, dryers and central AC use it, on a double-pole breaker. Learn more
5-15R outlet: The standard US household outlet: 120 V, 15 A, up to 1,800 W. Two flat slots plus a round or U-shaped ground hole. Learn more
5-20R outlet: A 120 V, 20 A outlet (up to 2,400 W). One slot is T-shaped, so it takes both 15 A and 20 A plugs. Standard on most generators. Learn more
Amp (A): How much electric current flows. Amps = watts ÷ volts, so a 20 A outlet on 120 V can carry up to 2,400 W. Learn more
Backfeeding (never do this): Feeding generator power into house wiring through a wall or dryer outlet, often with a 'double male' cord. Never do it: it can electrocute utility workers and start fires.
Bonded neutral: A generator whose neutral is connected to its frame. Some hookups need a bonded neutral and some a floating one; let your electrician decide.
BTU (British thermal unit): An amount of heat. AC sizes are in BTU per hour of heat removed. For heaters, 1 watt gives 3.412 BTU per hour. Learn more
CARB: The California Air Resources Board, which sets California's emission rules. A CARB-compliant generator is certified for sale in California.
Carburetor: The part that mixes fuel and air in a gas engine. Old gas left in it can gum it up, a common reason a generator won't start after sitting.
Choke: A lever that richens the fuel mix to help a cold engine start. Move it back to run once the engine warms up.
CO shut-off (CO sensor): A sensor that turns a gas generator off when carbon monoxide builds up around it. It's a backup only: it doesn't make indoor or garage use safe. Learn more
Conventional (open-frame) generator: A traditional generator that runs at a steady speed, usually on an open steel frame. It often has more watts and 240 V outlets, but rougher power and more noise.
Derate: To plan on less output than the label says. Generators make less power at high altitude, and dual-fuel models make less on propane.
Double-pole breaker: A breaker with two handles tied together that takes two slots in the panel. It feeds a 240 V circuit and trips both legs at once. Learn more
Dual fuel: A generator that can run on gasoline or propane. It usually makes a little less power on propane.
Duty cycle: The share of time an appliance actually runs. A fridge compressor cycles on and off, so its average watts are well below its running watts.
Eco mode: A setting on inverter generators that slows the engine to match the load, to save fuel and cut noise.
EER (energy efficiency ratio): An air conditioner's efficiency: BTU per hour of cooling for each watt it draws. Its running watts are roughly BTU ÷ EER. CEER and EER2 are newer versions. Learn more
EPA: The U.S. Environmental Protection Agency. Gas generator engines sold in the US must meet its emission standards; makers list this as EPA certified.
Floating neutral: A generator whose neutral isn't connected to its frame. It's normal on many portable generators, for RV use and for transfer switches that don't switch the neutral.
Fuel stabilizer: An additive that slows gasoline from going stale. It's used when gas will sit in a generator or fuel can for storage.
GFCI: Ground-fault circuit interrupter: an outlet or breaker that cuts power in a fraction of a second if current leaks to ground, to help prevent shocks.
Inlet box: An outdoor socket on your wall, wired to a transfer switch or interlock, where you plug in the generator's cord. An electrician installs it.
Interlock kit: A plate on your main panel that stops the main breaker and the generator breaker being on at the same time. It must be installed by a licensed electrician.
Inverter generator: A generator that makes clean power electronically (makers list 3% THD or less) and slows its engine at light loads, so it's quieter and uses less fuel.
Kilowatt-hour (kWh): 1,000 watt-hours. It's the unit on your power bill; a modern full-size fridge uses about 1 to 1.6 kWh a day. Learn more
L14-30 twist-lock: A 4-prong twist-lock carrying 120/240 V at 30 A (up to 7,200 W). The usual generator outlet for a home transfer switch or interlock. Learn more
L5-30 twist-lock: A 120 V, 30 A twist-lock (up to 3,600 W) with three curved blades: push in, then twist. Found on some generators and boat and RV cords. Learn more
LiFePO4 (LFP): Lithium iron phosphate, the battery type in most current power stations. It's known for a long cycle life and good heat stability.
Low-oil shutdown: A sensor that stops the engine when the oil gets too low, to protect it. Never bypass it; add the right oil instead.
MPPT: Maximum power point tracking: a solar charge controller that keeps adjusting to get the most power from your panels. Many power stations have one built in.
NMC: Nickel manganese cobalt, a lithium-ion battery type. It holds more energy per pound than LiFePO4 but usually lasts fewer charge cycles.
Parallel kit: Cables that link two compatible inverter generators so their power adds together. Some kits add a 30 A or a 240 V outlet.
Peak watts: The most a generator or power station can put out for a few seconds, to start motors. The same idea as starting or surge watts. Learn more
PGMA G300 and UL 2201: Safety standards for portable generators. CPSC says models certified to PGMA G300-2023 or UL 2201-2023 include carbon monoxide safety technology. Learn more
Rated (continuous) watts: The power a generator or power station can supply continuously. The same idea as running watts. Learn more
Running watts: The power an appliance uses once it's up and running, or the power a generator can supply hour after hour. Learn more
Soft start: A small device fitted to an AC's compressor that ramps the motor up gently. It cuts the start-up surge, so a smaller generator can start it.
Solar input and Voc: Voc is a solar panel's open-circuit voltage. Panels wired together must stay under the power station's maximum solar input voltage, and Voc rises in cold weather.
Spark plug: The part that makes the spark that lights the fuel in a gas engine. A dirty or worn plug is a common reason an engine won't start or runs rough.
Split-phase: How US homes get power: two 120 V hot legs and a neutral. One leg to neutral gives 120 V; leg to leg gives 240 V. Learn more
Starting (surge) watts: The extra burst of power a motor needs for a few seconds to start. Generators list it as starting, surge or peak watts. Learn more
THD (total harmonic distortion): How far power's wave shape is from a smooth sine wave. Lower is cleaner: inverters list 3% or less, standard generators about 12–20%. Learn more
Transfer switch: A switch, installed by a licensed electrician, that safely connects a generator to chosen house circuits and keeps it cut off from the utility lines.
Tri-fuel: A generator that can run on gasoline, propane or natural gas.
TT-30 (RV 30 amp): The 30 amp RV plug: 120 V, 30 A, up to 3,600 W, with two angled blades and a round ground pin. TT-30R is the outlet, TT-30P the plug. Learn more
UPS and pass-through: UPS mode switches your devices to battery almost instantly when the grid fails. Pass-through means a power station can run your devices while it charges.
Volt (V): Electrical pressure: the push behind the current. US household outlets are 120 V; big loads like well pumps use 240 V. Learn more
Watt (W): How fast something uses or makes power right now. Watts = volts × amps, so a 1,500 W heater on 120 V draws 12.5 amps. Learn more
Watt-hour (Wh): An amount of energy: 1 Wh is 1 watt used for 1 hour. Power station batteries are sized in watt-hours, like the size of a fuel tank. Learn more